05RC(Routing Protocol Configuration Guide)

User Manual - Configuration Guide (Volume 2)Versatile Routing Platform Table of Contents

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Table of Contents

Chapter 1 IP Routing Protocol Overview............................................................................. 1-1

1.1 Brief Introduction of IP Routing and Routing Table ...................................................... 1-1

1.1.1 Route and Route Segment (Hop) ..................................................................... 1-1

1.1.2 Routing with Routing Table .............................................................................. 1-2

1.2 VRP Routing Management Strategy ........................................................................... 1-31.2.1 Routing Protocol and Routing Priority ............................................................... 1-3

1.2.2 Load-sharing and Backup ................................................................................ 1-4

1.2.3 Multi-routing Protocols Sharing......................................................................... 1-4

Chapter 2 Configuration of Static Route.............................................................................. 2-1

2.1 Brief Introduction of Static Route................................................................................ 2-1

2.1.1 Static Route.................................................................................................... 2-1

2.1.2 Default Route.................................................................................................. 2-1

2.2 Configuring Static Route............................................................................................ 2-22.2.1 Static Route Configuration Task List................................................................. 2-2

2.2.2 Configure Static Route..................................................................................... 2-2

2.2.3 Configure a Default Route................................................................................ 2-3

2.3 Monitoring and Maintenance of Routing Table ............................................................ 2-3

2.4 Typical Configuration of Static Route.......................................................................... 2-62.5 Troubleshooting of Static Route Configuration ............................................................ 2-7

Chapter 3 Configuration of RIP............................................................................................ 3-1

3.1 Brief Introduction for RIP Protocol .............................................................................. 3-1

3.2 Configuring RIP ........................................................................................................ 3-23.2.1 RIP Configuration Task List ............................................................................. 3-2

3.2.2 Enable RIP Routing Process............................................................................ 3-3

3.2.3 Associate a Network with a RIP Routing Process .............................................. 3-4

3.2.4 Define a Neighboring Router............................................................................ 3-4

3.2.5 Specify a RIP Version...................................................................................... 3-53.2.6 Configure Check Zero Field of RIP Version 1.................................................... 3-5

3.2.7 Specify the Status of an Interface..................................................................... 3-6

3.2.8 Disable Host Routes........................................................................................ 3-6

3.2.9 Enable Route Summarization for RIP Version 2 ................................................ 3-6

3.2.10 Configure Authentication for RIP Version 2 ..................................................... 3-73.2.11 Enable Split-Horizon Mechanism.................................................................... 3-7

3.2.12 Enable Snapshot ........................................................................................... 3-9

3.2.13 Configure Route Redistribution for RIP ......................................................... 3-10

3.2.14 Specify Default Route Metric Value for RIP ................................................... 3-11

3.2.15 Specify Additional Route Metric Value for RIP ............................................... 3-11


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3.2.16 Set Route Preference.................................................................................. 3-11

3.2.17 Configure Route Distribution for RIP ............................................................. 3-12

3.2.18 Reset RIP ................................................................................................... 3-12

3.3 Monitoring and Maintenance of RIP.......................................................................... 3-133.4 Typical Configuration of RIP .................................................................................... 3-14

3.4.1 Configuring RIP Unicast ................................................................................ 3-14

3.4.2 Disabling RIP Split-Horizon............................................................................ 3-15

3.5 Troubleshooting of RIP ............................................................................................ 3-17

Chapter 4 Configuration of IGRP ......................................................................................... 4-1

4.1 Description of IGRP .................................................................................................. 4-1

4.2 Configuring IGRP...................................................................................................... 4-1

4.2.1 IGRP Configuration Task List........................................................................... 4-14.2.2 Enable IGRP Routing Process ......................................................................... 4-2

4.2.3 Associate a network with a IGRP routing process.............................................. 4-2

4.2.4 Configure the Current IGRP AS Number........................................................... 4-3

4.2.5 Define a Neighboring Router............................................................................ 4-4

4.2.6 Specify the Status of an Interface..................................................................... 4-44.2.7 Specify IGRP Metric Weights........................................................................... 4-5

4.2.8 Specify the Maximum Route Hop Count ........................................................... 4-6

4.2.9 Disable Route Holddown ................................................................................. 4-6

4.2.10 Disable Host Routes ...................................................................................... 4-7

4.2.11 Enable Split-Horizon...................................................................................... 4-74.2.12 Enable Snapshot ........................................................................................... 4-7

4.2.13 Configure Route Redistribution for IGRP......................................................... 4-8

4.2.14 Specify Default Route Metric Value for IGRP................................................... 4-8


4.2.16 Configure Route Filter for IGRP.................................................................... 4-104.2.17 Reset IGRP ................................................................................................ 4-11

4.3 Monitoring and Maintenance of IGRP ....................................................................... 4-11

4.4 Typical Configuration of IGRP.................................................................................. 4-12

4.4.1 Configure Default Metric for IGRP Routes Redistribution ................................. 4-12

4.5 Troubleshooting of IGRP ......................................................................................... 4-13

Chapter 5 Configuration of EIGRP ....................................................................................... 5-1

5.1 Brief Introduction of EIGRP........................................................................................ 5-1

5.2 Configuring EIGRP.................................................................................................... 5-35.2.1 EIGRP Configuration Task List ........................................................................ 5-3

5.2.2 Enable EIGRP Routing Process....................................................................... 5-3

5.2.3 Associate a Network with a EIGRP Routing Process ......................................... 5-4

5.2.4 Configure a Passive Interface .......................................................................... 5-4

5.2.5 Configure the Percentage of Bandwith Used by EIGRP ..................................... 5-55.2.6 Configure EIGRP Metric Weights ..................................................................... 5-6

5.2.7 Configure an Offset-list.................................................................................... 5-6


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5.2.8 Enable Route Automatic Summarization........................................................... 5-7

5.2.9 Enable Route Summarization of any Length Mask............................................. 5-7

5.2.10 Configure Authentication for EIGRP............................................................... 5-8

5.2.11 Configure Hello Interval and Hold Time Interval............................................... 5-85.2.12 Enable Split-Horizon...................................................................................... 5-9

5.2.13 Configure Route Redistribution for EIGRP....................................................... 5-9

5.2.14 Set Metric Value for EIGRP in a Route-map.................................................. 5-10

5.2.15 Configuring Default Metric of Redistributed Routes ........................................ 5-10

5.2.16 Set Route Preference.................................................................................. 5-105.2.17 Configure Route Filter for EIGRP ................................................................. 5-12

5.3 Monitoring and Maintenance of EIGRP ..................................................................... 5-13

5.4 Typical Configuration of EIGRP................................................................................ 5-14

5.4.1 Configure EIGRP Route Authentication .......................................................... 5-14

5.4.2 Configure EIGRP Timers ............................................................................... 5-165.4.3 Configure EIGRP Passive Interface............................................................... 5-17

5.4.4 Configuring EIGRP Route Summary............................................................... 5-19

5.5 Troubleshooting of EIGRP ....................................................................................... 5-20

Chapter 6 Configuration of OSPF ........................................................................................ 6-1

6.1 Brief Introduction to OSPF......................................................................................... 6-1

6.2 Configuring OSPF.................................................................................................... 6-3

6.2.1 OSPF Configuration Task List.......................................................................... 6-3

6.2.2 Specify Router ID............................................................................................ 6-36.2.3 Enable OSPF Routing Process ........................................................................ 6-4

6.2.4 Associate an Area-id with the Specified Interface .............................................. 6-4

6.2.5 Configure the OSPF Network Type................................................................... 6-5

6.2.6 Specify the Cost of Sending a Packet on an Interface........................................ 6-6

6.2.7 Specify the Router Priority ............................................................................... 6-66.2.8 Configure a Neighbor for NBMA Interface......................................................... 6-7

6.2.9 Specify Hello Interval....................................................................................... 6-8

6.2.10 Specify Dead Interval..................................................................................... 6-8

6.2.11 Specify Re-transmitting Interval...................................................................... 6-9

6.2.12 Specify Transmit-delay .................................................................................. 6-96.2.13 Configure the Route Cost Sent to an OSPF STUB Area................................. 6-10

6.2.14 Configure Route Summarization between OSPF Areas.................................. 6-10

6.2.15 Create and Configure a Virtual Link .............................................................. 6-11

6.2.16 Configure Authentication............................................................................. 6-12

6.2.17 Configure Route Redistribution for OSPF...................................................... 6-126.2.18 Configure Parameters when Redistributing External Routes........................... 6-13


6.2.20 Configure Route Filter for OSPF................................................................... 6-15

6.3 Monitoring and Maintenance of OSPF ...................................................................... 6-16

6.4 Typical Configuration of OSPF................................................................................. 6-17


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6.4.1 Configure OSPF on the Point-to-Multipoint Interface........................................ 6-17

6.4.2 Configure DR on OSPF Preference................................................................ 6-20

6.4.3 Configure OSPF Autonomous System............................................................ 6-22

6.4.4 Configure OSPF Virtual Link .......................................................................... 6-246.4.5 Configure OSPF Neighbor Authentication ....................................................... 6-26

6.5 Troubleshooting of OSPF Configuration ................................................................... 6-27

Chapter 7 Configuration of BGP .......................................................................................... 7-17.1 Brief Introduction of BGP........................................................................................... 7-1

7.2 Configuring BGP....................................................................................................... 7-2

7.2.1 BGP Configuration Task List............................................................................ 7-2

7.2.2 Enable BGP Routing Process .......................................................................... 7-3

7.2.3 Associate a network with a BGP routing process............................................... 7-37.2.4 Configure the BGP MED Metric........................................................................ 7-3

7.2.5 Allow the Comparison of the MED for Paths...................................................... 7-4

7.2.6 Change the Local Preference Value ................................................................. 7-4

7.2.7 Adjust BGP Timers.......................................................................................... 7-5

7.2.8 Configure Neighbors ....................................................................................... 7-67.2.9 Configure BGP Peer Groups ............................................................................ 7-9

7.2.10 Create an Aggregate Addresses .................................................................. 7-14

7.2.11 Configure a Route Reflector......................................................................... 7-14

7.2.12 Create a Community List for BGP................................................................. 7-16

7.2.13 Configure a BGP Routing Domain Confederation ......................................... 7-177.2.14 Configure Route Dampening........................................................................ 7-18

7.2.15 Configure Synchronization of BGP and an IGP.............................................. 7-21

7.2.16 Configure the Interaction between BGP and an IGP ...................................... 7-22

7.2.17 Define an Access-list Entry, an AS Path-list Entry, a Route-Map..................... 7-22

7.2.18 Configure Route Filter for BGP..................................................................... 7-257.2.19 Reset BGP Connections .............................................................................. 7-25

7.3 Monitoring and Maintenance of BGP ........................................................................ 7-26

7.4 Typical Configuration of BGP................................................................................... 7-27

7.4.1 Configuring AS Confederation Attribute .......................................................... 7-27

7.4.2 Configuring BGP Route Reflector................................................................... 7-297.4.3 Configuring BGP Path Selection..................................................................... 7-31

Chapter 8 IP Routing Protocol-Independent Configuration ................................................. 8-1

8.1 Brief Introduction of IP Routing Protocol-Independent Features................................... 8-18.2 Configuring IP Routing Protocol-Independent ............................................................. 8-2

8.2.1 IP Routing Protocol-Independent Configuration Task List .................................. 8-2

8.2.2 Define a Route-map ........................................................................................ 8-3

8.2.3 Define a Matching Rules.................................................................................. 8-3

8.2.4 Define a Setting Clause................................................................................... 8-48.2.5 Configure Route Redistribution......................................................................... 8-5

8.2.6 Define a Prefix-List Entry ................................................................................. 8-6


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8.2.7 Configure Route Filter ..................................................................................... 8-8

8.3 Monitoring and Maintenance of IP Routing Protocol-Independent Features................... 8-9

8.4 Typical Configuration of IP Routing Protocol-Independent Features ............................ 8-10

8.4.1 Configure Filtering Route Information Received.............................................. 8-108.4.2 Configure Filtering Route Information for OSPF............................................... 8-11

8.4.3 Configure Filtering Route Information............................................................. 8-12

8.5 Troubleshooting of IP Routing Protocol-Independent Features ................................... 8-13

Chapter 9 Configuration of IP Policy Routing...................................................................... 9-1

9.1 Brief Introduction of IP Policy Routing.......................................................................... 9-1

9.2 Configuring IP Policy Routing..................................................................................... 9-1

9.2.1 IP Policy Routing Configuration Task List ......................................................... 9-1

9.2.2 Create a Route-map........................................................................................ 9-19.2.3 Define Match Rules ......................................................................................... 9-2

9.2.4 Define Set Clause........................................................................................... 9-2

9.2.5 Enabling/Disabling Local Policy Routing ........................................................... 9-3

9.2.6 Enable/Disable Policy Routing on the Interface ................................................. 9-3

9.3 Monitoring and Maintenance of IP Policy Routing........................................................ 9-39.4 Typical Configuration of IP Policy Routing................................................................... 9-4

9.4.1 Configure Policy Routing Based on Source Address.......................................... 9-4

9.4.2 Configuring Policy Routing Based on Message Size.......................................... 9-5

User Manual - Configuration Guide (Volume 2)Versatile Routing Platform

Chapter 1IP Routing Protocol Overview

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Chapter 1 IP Routing Protocol Overview

1.1 Brief Introduction of IP Routing and Routing Table

1.1.1 Route and Route Segment (Hop)

Routers are used to select routing in the Internet. A router selects a suitable path (via anetwork) according to the destination host address contained in a received data packet,and sends the data packet to the next router. The last router on the path will send thedata packet to the destination host.

Router regards the path that a packet goes through In a network (from entering thenetwork until leaving it) as a logical route unit, which is called a Hop. For example, inthe diagram below, a packet from host A to host C passes altogether 3 networks and 2routers, i.e., a total of 3 hops. It shows that when two nodes are connected to eachother via a network, they are separated by one hop and are neighbors on the Internet.Similarly, two adjacent routers are those connected to the same network. So, the countof hops from a router to the local network host will be 0. In the diagram, the bold arrowsrepresent the hops. The router does not care about how many physical links are therein each route unit.

:

B:

C

:

A

R R

Route Segment

RR

R

Figure RC -1-1 Concept of route segment (hop)

As networks may vary in size, and the actual length of each hop is also different.Therefore, for different networks, the route segments can be multiplied by a weightcoefficient and then used to measure the length of a path.

If a router in the Internet is regarded as a node on the network, and a hop in the Internetis regarded as a link, then routing in the Internet will be similar to that in a simplenetwork. Sometimes it may not be ideal to select the route with the fewest hops. Forexample, a route passing 3 LAN hops might be much faster than a route passing 2WAN hops.



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1.1.2 Routing with Routing Table

Routing table is essential for a router to transfer data packets. Every router has onerouting table. The routing item in routing table shows which physical port of the routershould be used to transfer a data packet to a sub-network or a host, so that the packetcan reach the next router on this path, or reach the directly connected destination hostwithout passing other router.

The routing table consists of the following key items:

l Destination address: used to identify the destination address or destination

network of IP packets.

l Network mask: used, together with the destination address, to identify the address

of the route segment where the destination host or router is located. Logical “and”

the destination address and network mask to get the address of the route segmentwhere the destination host or router is located. For example, if the destination

address is 129.102.8.10 and mask is 255.255.0.0, the address of the route

segment where the destination host or router is located is 129.102.0.0. The mask

consists of several consecutive “1”s and “0”s, which can be expressed with dotted

decimal system or with the number of consecutive “1”s in the mask.l Output interface: indicates the interface of the router from which the IP packet is

forwarded.

l Next hop IP address: indicates the next router the IP packet will be forwarded.

l The priority of this route added to IP routing table: there may be different next hops

to the same destination. These routes may be found by different routing protocolsor they may be static routes configured manually. The route with higher priority

(smaller value) will be the best route. The user can configure multiple routes with

different priorities to the same destination and select one to forward messages.

According to the destination of a route, it can be classified as:

l Sub-network route: the route whose destination is a sub-network

l Host route: the route whose destination is a host

According to the connection mode between the destination and the router, you canclassify the router as:

l Direct route: network of the destination is directly connected to the router.

l Indirect route: network of the destination is not directly connected to the router.

To keep the routing table within a certain size, set a default route. Whenever a datapacket fails to find the routing table, select the default route to transfer.

In complicated networks, the digits in each network are its network address. Forexample, router 8 (R8) is connected to three networks, so it has 3 IP addresses and 3physical ports. The routing table is shown in the figure below.



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The network ofdestination

hostthe message is

The router wheretransferred

The port tobe passed

10.0.0.0 Direct 211.0.0.0 Direct 112.0.0.0 11.0.0.2 13.0.0.0 Direct 314.0.0.0 13.0.0.2 315.0.0.0 10.0.0.2 216.0.0.0 2

15.0.0.0

16.0.0.0

10.0.0.0

13.0.0.0

12.0.0.0

14.0.0.011.0.0.0

R 4R 1

3

R2

R6

R 5

R7

R 81

11.0.0.2

2

12.0.0.1

12.0.0.2

12.0.0.314.0.0.1

14.0.0.213.0.0.1

13.0.0.411.0.0.1

310.0.0.1

10.0.0.2

16.0.0.316.0.0.2

15.0.0.2

15.0.0.1 13.0.0.2

16.0.0.2

13.0.0.3

Routing table of Router R8

10.0.0.2

1

R

Figure RC-1-2 Routing table illustration

VRP supports not only static route configuration, but also dynamic routing protocolssuch as RIP, IGRP, EIGRP, OSPF and BGP. Besides, according to interface status anduser configuration, a router can automatically obtain some direct routes during theiroperation.

1.2 VRP Routing Management Strategy

VRP supports both manual configuration of a static route to a specific destination anddynamic routing protocol configuration to interact with other routers in the network,which find a route with the routing algorithm. Both the static route configured by theuser and dynamic route found by the routing protocol are uniformly administered inVRP. Routers found or configured between static routes and routing protocols can beshared.

1.2.1 Routing Protocol and Routing Priority

Different routing protocols (including static routes) may find different routes to the samedestination, but not all these routes are optimal. In fact, at a certain moment, the currentroute to a destination is determined only by a unique routing protocol. As a result, everyrouting protocol (including static route) is assigned a priority. When there are multipleroute information sources, the route found by higher-priority routing protocols willbecome current route. The routing protocols and their default routing priorities (the lessthe value, the higher the priority) are shown in the table below.

Here, 0 stands for directly connected route and 255 for any route from unknownsources or terminals.



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Table RC-1-1 Routing protocol and routing priority

Routing protocol or type Corresponding routing priority

Connected 0OSPF 10Internal EIGRP 50STATIC 60IGRP 80RIP 100IBGP 130OSPF ASE 150External EIGRP 170EBGP 170Unknown 255

Except for the direct route (Connected), the priority of each dynamic routing protocolcan be manually configured as per requirement. In addition, each static route can havea different priority.

1.2.2 Load-sharing and Backup

l Load sharing: Support multi-route mode, i.e. the configuration of multiple routes of

the same priority to the same destination. If there is no route of higher priority to

the same destination, the routes of the same priority will all be accepted by IP.

When forwarding messages to the destination, IP will forward the message via

these routes in turn so as to achieve load sharing on the network.l Route backup: VRP supports route backup. When the backup line changes,

automatic route switchover will take place to enhance network reliability.

To realize route backup, among the multiple routes to the same destination, you can setthe highest priority to the route passing the main path, and set lower priority to theroutes passing backup paths. Then, normally the route will send data through the mainpath. When a fault occurs to the line, the route will hide itself automatically, and selectone backup route of highest priority for data transmission. In this way, the maininterface is switched over to the backup interface. When the main path is recovered,the router will recover the corresponding route and begin reselecting route. Since therecovered is of the highest priority, it will select this main route to transmit data. This isthe automatic switchover from backup interface to main interface.

One routing protocol may find several different routes to the same destination. If thisrouting protocol is of the highest priority among all the active routing protocols, all theroutes it found will be taken as currently effective routes. In this case, the load sharingof IP traffic on the routing protocol layer is guaranteed. At present, routing protocolssupporting load sharing include static routes, OSPF and EIGRP. To the samedestination, there can be a maximum of 3 effective routes.

1.2.3 Multi-routing Protocols Sharing

As different protocols may find different routes due to various algorithms adopted byeach protocol, the problem of sharing the findings of different protocols is of concern.VRP supports redistributing routes found by one routing protocol to another protocol.Each protocol has its own route redistribution mechanism.


Chapter 2Configuration of Static Route

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Chapter 2 Configuration of Static Route

2.1 Brief Introduction of Static Route

2.1.1 Static Route

Static route is a special route, manually configured by administrator. Through theconfiguration of a static route, the router can work normally in a simple network thatonly has one path to a specified destination. Proper setting and application of the staticroute can guarantee network security effectively, at the same time, ensure bandwidthfor important applications.

There is a problem: If the topology changes due to network failure or other problems,the static route cannot change automatically and requires the intervention ofadministrator.

The static route has the following attributes:

l Reachable route: normally all routes are reachable, i.e., an IP packet is sent to the

next hop according to the route identified by the destination -- a commonapplication of static routes.

l Unreachable route: when a static route to a certain destination has "reject"

attribute, all IP packets to this destination will be discarded and destination

unreachable information is given.

l Black hole route: when a static route to a certain destination has "black hole"attribute, all IP packets to this destination will be discarded.

Here, attributes "reject" and "blackhole" are normally used to control the scope ofdestinations reachable by this router, so as to facilitate network fault diagnosis.

2.1.2 Default Route

Default route is one type of static routes. In short, default route is used when nomatching route is found or when there is no suitable route. In the routing table, thedefault route is the route to network 0.0.0.0 (mask is 0.0.0.0). You can check whetherthe default route is properly set through the result of show ip route command. If thedestination address of the message does not match any route item in the routing table,the default route will be selected. And if there is no default route at this time, thismessage will be discarded and an ICMP message will be returned to the sourceterminal, indicating that the destination address or network is unreachable.

Default route is very useful in network. In a typical network with hundreds of routers,dynamic routing protocol may consume lots of bandwidth resource. Use default routemeans replacing link of high bandwidth with link of adequate bandwidth, so as to meetthe requirements of communication for large number of subscribers.



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2.2 Configuring Static Route

2.2.1 Static Route Configuration Task List

Static route configuration tasks are listed as follows:

l Configure a static route

l Configure a default route

2.2.2 Configure Static Route

Perform the following task in global configuration mode.

Table RC-2-1 Configure a Static Route

Operation Command

Configure a static route ip route ip-address { mask | mask-length } { interface-type interface-number |nexthop-address } [ preference value ] [ reject | blackhole ]

Delete a static route no ip route ip-address { mask | mask-length } [ interface-type interface-number |nexthop-address ] [ preference value ]

The explanation of each parameter is as follows:

1) IP address and network mask

IP address is of dotted decimal. As it is required that the 1s in the 32 bit mask must becontinuous, the mask can also be presented in the dotted decimal format, or by themask length (i.e., digits of “1”s in the mask) to represent.

2) Transmitting interface or next hop address

In the configuration of static routes, the transmitting interface interface-type interfac-number or the next hop address nexthop-address can be designated as required by theactual conditions.

You can specify the transmitting interfaces in the following cases:

l For interfaces that support resolution from the network address to the link layer

address (like Ethernet interface supporting ARP), if a host address has beenspecified for Ip-address and mask (or mask-length), and if the destination address

is in a network directly connected to this interface, then you can specify the

transmitting interface.

l For a point-to-point type interface, specifying the transmitting interface implies

specifying the address of next hop. In this case, the address of the remoteinterface is considered the address of next hop. If the serial port is encapsulated

with the PPP protocol, and gets the IP address of the opposite side through PPP

consultation, then you only need to specify the transmitting interface instead of the

address of next hop.

When NBMA interfaces like the interface encapsulated with X.25 or frame relay ordial-up interface support point-to-multipoint mode, besides configuring IP route, youshall also set up secondary route at the link layer, i.e., mapping from the IP address to



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the link layer address (such as dialer map ip, x.25 map ip or frame-relay map ipcommands, etc). In this case, you cannot specify the transmitting interface for staticroute and shall configure the IP address of next hop.

Actually, all of the route items must mark the address of next hop. According to thedestination address of packets, IP searches for the matching route in the routing table.Only when the address of next hop is specified in the route, can the link layer findcorresponding address through this address and transfer packets.

However, in certain cases (such as PPP encapsulated in link layer), address of theopposite side may be unknown when the router is configured so that the sendinginterface have to be specified. In addition, if the sending interface has been specified, itis not necessary to change the router’s configuration when the opposite side’s addresschanged.

3) Preference

Different configuration of preference can achieve flexible route management. Forexample, when configuring multiple routes a network destination, if the samepreference is designated, load sharing can be realized. If different preferences aredesignated, route backup can be realized.

4) Other parameters

reject and blackhole refer to unreachable routes and black hole routes respectively.

2.2.3 Configure a Default Route


Table RC-2-2 Configure a Default Route

Operation Command

Configure a default route ip route 0.0.0.0 { 0.0.0.0 | 0 } { interface-type interface-number | nexthop-address } [ preference value ] [ reject | blackhole ]

Delete a default route no ip route 0.0.0.0 { 0.0.0.0 | 0 } [ interface-type interface-number | nexthop-address ] [ preference value ]

The parameters of this command mean the same as those in static route configuration.

2.3 Monitoring and Maintenance of Routing Table

Table RC-2-3 Monitoring and maintenance of routing table

Operation Command

Show the abstract information of the routing table show ip routeShow the information of specific route show ip route ip-addressShow the detailed information of the routing table show ip route detailShow the radix information of the routing table show ip route radixShow the static routing table show ip route static

1) Show information of the routing table

Quidway# show ip route



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Routing Tables:

Destination/Mask Proto Pref Metric Nexthop Interface

127.0.0.0/8 Static 0 0 127.0.0.1 loopback

127.0.0.1/32 Direct 0 0 127.0.0.1 loopback

138.102.128.0/17 Direct 0 0 138.102.129.7 Ethernet 0

202.38.165.0/24 ospf 0 0 202.38.165.1 Serial 1

The above information indicates the destination address/mask length, routing protocoltype (Static stands for static route and Connected for directly reachable route), thepreference of the route, metric value, next hop address and forwarding interface.

2) Show information of specified route

Quidway# show ip route 127.0.0.1

**Destination: 127.0.0.1 Mask: 255.255.255.255

Protocol: *Connected Preference: 0

NextHop: 127.0.0.1 Interface: 127.0.0.1(LO0)

State: <NoAdv Int Active Retain>

Age: 114:03:05 Metric: 0/0

This command shows all information of the route to a specific destination IP address.The output information can help the user to identify whether there is the specified routeor whether the route is correct.

If a natural network is specified, such as 10.0.0.0, the detailed information of all theroutes in this network will be displayed. Otherwise, only the route information of thespecified address will be displayed.

3) Show detailed information of the routing table

Quidway# show ip route detail

Route state description

NoAdv: do not advertise Int: AS Interior route

Ext: AS External route Del: route to be deleted

Active: current route Retain: route retains in the routing table

Rej: rejecting route Black: black hole route

Routing Tables:

Generate Default: no

+ = Active Route, - = Last Active, * = Both

Destinations: 4 Routes: 4

Holddown: 0 Delete: 9 Hidden: 0


Protocol: *Static Preference: 0


State: <NoAdv Int Active Retain Rej>

Age: 19:31:06 Metric: 0/0


Protocol: *Connected Preference: 0




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State: <NoAdv Int Active Retain>

Age: 114:03:05 Metric: 0/0

Meanings of respective parameters are described in the following table:



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Table RC-2-4 Meanings of parameters in show ip route detail command field

Category Symbol Meaning

NoAdv NOADVISE routing is not distributed when a routing protocol publishes route tothe outside according to strategy.

Int This route is found by the internal gateway protocol (IGP).Ext This route is found by the external gateway protocol (EGP).Del Route already deleted.Active Really valid route.Retain Normally, when a routing protocol exits normally, it will delete all the routes it

has found, except those marked with Retain.

RejThis route does not guide the packet transfer like normal routes. Routes markedREJECT will discard the packets that select this route, and send ICMPunreachable packet to the packet source. The REJECT route is normally usedfor network testing.

Descriptionof routestatus

Black The BLACKHOLE route is similar to the REJECT route, except that it omits thestep of sending the ICMP unreachable packet to the packet source.

Holddown

Holddown route refers to a route announcement strategy in some distancevector routing protocols (e.g., RIP) to avoid the diffusion of error routes, andensure rapid, accurate spreading of route unreachable information. It usuallyannounces fixedly a route at a certain time interval regardless of the change onthe route currently found to the same destination. For details, refer to specificrouting protocols. Shown in the routing table is the number of current Holddownroutes.

Delete Current routes deleted.

Statisticinformationof routingtable

HiddenSome routes temporarily unreachable due to certain reasons (such as interfaceDown), which should not to be deleted, can be hidden so as to be restored later.What is shown in the routing table is the number of routes currently hidden.

4) Show static routing table

Quidway# show ip route static

Static routes for family INET: (* indicates gateway(s) in use)

1.2.3.0/24 pref 60 <Int> intf Enthernet 0

127.0.0.0/8 pref 0 <NoAdv Int Retain Rej> intf 127.0.0.1

The above information helps the user to identify whether the static route configurationis correct. It shows the destination address/mask length, route preference, <statusparameter> and output interface or next hop address.

If the route of a natural segment is specified, such as 10.0.0.0, then the detailedinformation of all routes in network segment will be shown. Otherwise only the routeinformation of the specific address will be shown.

2.4 Typical Configuration of Static Route

I. Networking requirements

Through configuring a status route, any two hosts or routes can communicate witheach other.



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II. Networking diagram

Host 11.1.1.1

Host 2

Router3

sl01.1.2.2

Host 31.1.5.1

en01.1.5.2

sl11.1.3.1

sl01.1.2.1

sl01.1.3.2en0

1.1.1.2Router1 Router2

en01.1.4.1

1.1.4.2

Figure RC-2-1 Networking diagram of static route configuration example

III. Configuration procedure

! Configure the static routes for Router1:

Quidway(config)# ip route 1.1.4.0 255.255.255.0 1.1.6.2








2.5 Troubleshooting of Static Route Configuration

Fault 1: The status of physical interface and link layer protocol are both UP, but IPpackets can not be forwarded normally.

Troubleshooting:

l Use the show ip route static command to check whether related static routes are

configured correctly.

l Use the show ip route command to see whether this static route is already

effective.

l Check whether the next hop address is specified or specified correctly on theNBMA type interface.

l Check the secondary routing table of the link layer on the NBMA interface to see if

the configuration is correct.


Chapter 3Configuration of RIP

3-1

Chapter 3 Configuration of RIP

3.1 Brief Introduction for RIP Protocol

Routing Information Protocol (RIP) is a relatively old and simple dynamic routingprotocol, but is widely used in practice. RIP is protocol based on a Distance-Vector(D-V) algorithm, which exchanges routing information through UDP (User DatagramProtocol) packets, and updates route message in every 30s. If a router does notreceive any route-updating message from other routers in 180 seconds, the routingitem will be labeled as unreachable and will be deleted if still no updating message isreceived 120 seconds after that period.

RIP uses Hop Count (also called Routing Metric) to measure the distance to thedestination router. In RIP, the hop count from a router to its directly connected networkis 0, and the hop count from one router to a network via another router is 1, and so on.To restrict the convergence time, RIP stipulates that the metric is an integer from 0 to 15.If the hop count is greater than or equal to 16, then it is considered infinitely large, i.e.destination network host is unreachable.

RIP has two versions RIP-1 and RIP-2, among which RIP-2 supports plain textauthentication and MD5 authentication, as well as the variable-length sub-net masks.

To improve the performance and prevent route loop, RIP support Split-horizon,Poisoned Reverse and uses Triggered Update, and allows the redistribution of routesobtained by other routing protocols.

Each router running RIP manages a database, which includes route items of allreachable routers on the network. A route item includes the following information.

l Destination address: the address of the host or network.

l Next-hop address: the address of the next router that this router will pass to get to

the destination.l Interface: the interface where messages are forwarded.

l Metric value: the overhead for the router to get to the destination. It is an integer

ranging from 0 to16.

l Timer: the last time when the route item is modified.

l Route tag: the tag indicating whether it is an internal routing protocol route or anexternal routing protocol route.

The procedure of running a RIP rou�ting process can be described as follows:

1) When a specific router is first starting a RIP routing process, it broadcasts request

messages to the neighbor routers. After receiving the request messages, the

neighbor routers respond to the request and return response messages including

local routing information.2) After receiving the response message, the router will modify the local routing table

and send triggered modified messages to the neighboring routers, broadcasting

the route modification information. After receiving the triggered modified message,



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the neighbor routers will forward them to its neighbors. After a series of triggered

modification broadcasting, all routers can receive and maintain the latest routing

information.

3) At the same time, RIP broadcasts the local routing table to the neighbor routers

every 30 seconds. The neighbor routers receive the message and maintain thelocal routes. Then they will select the best route to broadcast the modification

information to their neighbor networks. In this way the updated routing information

can be globally effective. Also, RIP applies a timeout mechanism to dispose

outdated route and make sure the route is real-time and effective.

Though RIP is widely used by most of the router manufacturers, it has considerablelimitation:

l It supports very limit number of routers: So RIP is only suitable to small

autonomous system, such as, most campus networks and local networks withsimple structure and high continuity.

l It calculates route depending on fixed metric: RIP cannot update its metric in real

time to adapt network’s change. The metric defined by administrator remains till

updated artificially.

l It may cost a considerable network bandwidth to update its information: RIPbroadcasts updating message per 30 seconds. So it may cause low efficiency in a

network with a lot of nodes.

3.2 Configuring RIP

3.2.1 RIP Configuration Task List

In all the configuration tasks, first enable RIP routing process and Associate a networkwith a RIP routing process, then configure other functional features related to RIPprotocol. Configuring the interface-related features is not subject to whether a RIProuting process has been enabled. It should be noted that the original interfaceparameters become invalid after the RIP routing process is closed.

RIP configuration tasks are listed as follows:

l Enable RIP Routing Process

l Associate a network with a RIP routing process

l Define a neighboring router

l Specify a RIP Versionl Configure Check Zero Field of RIP-1

l Specify the Status of an Interface

l Disable Host Route

l Enable Route Summarization

l Configure Authentication for RIP Version 2l Enable Split-Horizon Mechanism

l Enable Snapshot



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l Configure Route Redistribution for RIP

l Specify Default Route Metric Value for RIP

l Specify Additional Route Metric Value for RIP

l Specify RIP Preference

l Configure Route Distribution for RIPl Reset RIP

3.2.2 Enable RIP Routing Process

You have to first enable RIP routing process to enter RIP protocol configuration mode,then configure parameters related to RIP protocol, while for the interface-relatedparameters, will not subject to whether a RIP routing process has been enabled.




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Table RC-3-1 Enable a RIP Routing Process

Operation Command

Enable a RIP routing process and enter the RIP protocolconfiguration mode router rip

Turn off a RIP routing process no router rip

By default, RIP routing process is not enabled.

The parameters related to an interface will be also invalid after a RIP routing process isturned off.

3.2.3 Associate a Network with a RIP Routing Process

To flexibly control RIP operation, you can configure corresponding network segment toRIP network so that RIP messages can be received and transmitted through thespecified interface.

Perform the following task in RIP protocol configuration mode.

Table RC-3-2 Associate a Network with a RIP Routing Process

Operation Command

Specify a lists of networks associated with a RIP routing process network {network-number | all }Delete a lists of networks associated with a RIP routing process no network {network-number | all }

No network is associated with RIP routing process by default after RIP routing processis enabled.

After enable a RIP routing process, you should specify a lists of networks with the RIProuting process, since RIP only works on the interface of specified network segment.RIP won’t receive or forward route on interfaces of non-specified network segments, asif these interfaces did not exist. network-number is the address of the enabled ordisabled network or it can be the network address of the interfaces.

When network command is used to a specified address, the interface of the networksegment of this address will be enabled. For example: network 129.102.1.1, use eithershow running-config or show ip rip command, you can see network 129.102.0.0.

3.2.4 Define a Neighboring Router

RIP is a broadcast protocol. It exchanges routing information with non-broadcastingnetworks in unicast mode.


Table RC-3-3 Define a Neighboring Router

Operation Command

Define a neighboring router with which to exchange routing information neighbor ip-addressRemove a neighboring router with which to exchange routing information no neighbor ip-address



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By default, no neighboring routers are defined.

Normally, this command is not recommended because the opposite side does not needto receive two identical packets at the same time. Also when a neighbor sendsmessages, it is also subject to the restrictions of such commands as ip rip work, ip ripout, ip rip in and network.

3.2.5 Specify a RIP Version

RIP-2 has 2 transmission modes: broadcast and multicast. Multicast is the defaultmode. The multicast address in RIP-2 is 224.0.0.9. One of the advantages of themulticast mode is that the hosts that do not run RIP in this network will not receive thebroadcast packets. Additionally, hosts running RIP-1 will be prevented from receivingand processing the RIP-2 routes with subnet masks.

When the interface is specified to use RIP-1, only RIP-1 and RIP-2 broadcast packetswill be received. In this case, RIP-2 multicast packets will be rejected. When theinterface is specified to use RIP-2 broadcast, only RIP-2 broadcast packets will bereceived. In this case, RIP-2 multicast packets will be rejected. When the interface isspecified to use RIP-2 multicast, only RIP-2 multicast packets will be received. In thiscase, RIP-1 and RIP-2 broadcast packets will be rejected.

Perform the following task in interface configuration mode.

Table RC-3-4 Specify a RIP Version

Operation Command

Specify the interface receive and send only RIP Version 1 ip rip version 1Specify the interface receive and send only RIP Version 2 ip rip version 2 [ bcast | mcast ]Restore the default RIP version run on the interface no ip rip version

RIP-1 is the default version used on the interface. The interface running RIP-1 canreceive both RIP-1 and RIP-2 broadcast packets. When RIP-2 is used on the interface,multicast is the default mode.

3.2.6 Configure Check Zero Field of RIP Version 1

RFC1058 stipulates that some field in RIP Version 1 message header must be zero,which is called Zero Field. Therefore if the interface version is set to RIP Version 1,perform zero field check to the message, otherwise the message will be rejected. Thereis no zero field in RIP-2, so this configuration is invalid in RIP-2.


Table RC-3-5 Configure Check Zero Field of RIP Version 1

Operation Command

Enable check zero field of RIP version 1 checkzeroDisable check zero field of RIP version 1 no checkzero

RIP VERION 1 enables zero field check by default.



3-6

3.2.7 Specify the Status of an Interface

You can specify the working status of RIP on interface, such as whether RIP is runningon the interface, i.e. whether RIP refreshed messages are transmitted and received onthe interface. You can also specify separately whether updated messages should betransmitted or received on the interface.


Table RC-3-6 Specify the Status of an Interface

Operation Command

Specify running RIP on the interface ip rip workDisable running RIP on the interface no ip rip workSpecify receiving RIP update packets on the interface ip rip inputDisable receiving RIP update packets on the interface no ip rip inputSpecify sending RIP update packets on the interface ip rip outputDisable transmitting RIP updated packets on the interface no ip rip output

By default, an interface can both receive and send RIP update packets.

no ip rip work command is similar to no network command in that the interface usingeither command no longer tranceives RIP route. They differ in that in no ip rip workmode, routes of related interfaces are forwarded and in no network mode, routes ofrelated interfaces are not forwarded, as if an interface was missing.

In addition, ip rip work functions similar to the combination of two commands ip ripinput and ip rip output.

3.2.8 Disable Host Routes

In some special cases, router may receive large number of host routes from the samenetwork segment. These routes occupy lots of network resources and are of less use toroute addressing. You can configure disable host route function to reject receiving thehost routes.


Table RC-3-7 Disable a Host Route

Operation Command

Disable receiving host routes no host-routeEnable receiving host routes host-route

By default, the router is enabled to receive the host routes.

3.2.9 Enable Route Summarization for RIP Version 2

Route summary means: the routes of different sub-networks in the same naturalnetwork segment will be sent (to other network segments) as a summarized route witha natural mask. Route summary reduces the routing information in the routing table andreduces switching information.



3-7

RIP-1 always sends routes with natural mask. RIP-2 supports sub-net mask and routeof unknown category. But if the sub-net route needs to be broadcast, RIP-2 routesummary function can be disabled.


Table RC-3-8 Enable Route Summarization

Operation Command

Enable automatic route summarization auto-summaryDisable automatic route summarization no auto-summary

By default, RIP-2 automatic route summarization is enabled.

3.2.10 Configure Authentication for RIP Version 2

RIP Version 1 does not support authentication for packets. But when RIP Version 2supports authentication.

RIP Version 2 supports authentication in two modes: plain text authentication and MD5authentication. Security is not ensured in plain text authentication. Plain text meansthat unencrypted authentication is transmitted with the packets, therefore plain textauthentication does not apply to high confidentiality. The MD5 authentication has twomessage formats, in compliance of the requirements of RFC1723 (RIP Version 2Carrying Additional Information) and RFC2082 (RIP Version 2 MD5 Authentication)respectively.

Quidway series routers support both formats.


Table RC-3-9 Configure Authentication for RIP Version 2

Operation Command

Specify a password for RIP Version 2 plain text authentication ip rip authentication simple passwordSpecify a key-string for RIP Version 2 MD5 authentication ip rip authentication md5 key-string string

Specify the packet type of MD5 authentication for RIP Version 2 ip rip authentication md5 type [cisco |usual]

Cancel authentication for RIP Version 2 no ip authentication

By default, RIP Version 2 packets will not be authenticated at an interface. If the packettype of MD5 authentication is not specified, use cisco type.

3.2.11 Enable Split-Horizon Mechanism

RIP is a D-V algorithm routing protocol. It uses the split-horizon algorithm to avoid looproute. Split-horizon means that routes received at a certain interface are not sent fromthe same interface. Usually, it is enabled. But in some special circumstances, split-horizon shall be disabled, sacrificing efficiency for correct transmission of routes.

It is not recommended to disable the RIP split-horizon by user.

Disabling split-horizon mechanism is not effective on point-to-point connection links.



3-8




3-9

Table RC-3-10 Enable Split-Horizon Mechanism

Operation Command

Enable split-horizon mechanism ip rip splitDisable split-horizon mechanism no ip rip split

By default, split-horizon mechanism is enabled on the interface.

3.2.12 Enable Snapshot

I. Working principle of snapshot

The snapshot function of RIP is an improvement on bandwidth seizure and overheadcaused by periodic forwarding of D-V protocol. It is mainly used in Dial-On-Demandnetwork.

First select the network that needs the function, then configure the snapshot functionon the corresponding interfaces of all the routers connected to this network. Then,select one router connected to this network, and configure its corresponding interfaceas Client, while the interfaces of all other routers are configured as Server. The Clientinitiates message switching, and decides the route switching frequency.

When the interface is configured as a Snapshot, time will be divided into active periodand quiet period, and route switching occurs only in active periods. When active periodcomes, set the corresponding route timeout, clear Quiet timer and set Active timer.Then Client will send route-updating messages to all Servers. When the serversreceive route-updating message, they will activate themselves and enter the activeperiod for normal route switching between the routers. At the end of the active period,the routers save all the snapshot route items as snapshots. These route items will nottimeout within the subsequent quiet period. At the end of the quiet period, anotheractive period will begin, and the new message switching begins. The diagram belowshows the state transition diagram of the snapshot function.

Figure RC-3-1 State-Transition diagram of snapshot function

II. Configure snapshot at client

At the client terminal, two time segments should be configured. One is the active-interval and the other quiet-interval.




3-10

Table RC-3-11 Configure snapshot at client

Operation Command

Specify the duration of active interval and quiet interval at server ip rip snapshot client active-interval quiet-interval

Delete the duration of active interval and quiet interval at server no ip rip snapshot client

By default, snapshot is disabled. The duration of active interval should be at least 3minutes longer than that of quiet interval.

III. Configure snapshot at server

Configuration of snapshot at server needs only one active period. The clientdetermines other time segments. Please note that the active period at the servershould be the same as that at the client during configuration.


Table RC-3-12 Configure snapshot at server

Operation Command

Specify the duration of active interval at client ip rip snapshot server active-intervalDelete the duration of active interval at client no ip rip snapshot server

By default, snapshot mechanism is disabled on the interface.

3.2.13 Configure Route Redistribution for RIP

RIP permits to redistribute the routes from routing domain into the routing table.


Table RC-3-13 Routing redistribution for RIP

Operation Command

Configure route redistribution for RIP redistribute protocol [ metric metric ] [ route-mapmap-name ]

Cancel route distribution for RIP no redistribute protocol

By default, RIP does not redistribute routes from other domain into the routing table.

protocol specifies the source routing domain that can be redistributed. At present, ripcan redistribute routes domain such as connected, static, igrp, eigrp, ospf, ospf-aseand bgp.

Please refer to the section “Configure Route Redistribution from Another RoutingDomain” in “Configure IP routing Protocol-Independent Features” for the details ofrouting redistribution.



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3.2.14 Specify Default Route Metric Value for RIP

Command redistribute is used to redistribute other routing protocols. If redistribute isnot followed by the value of routing metric, then regard the parameter value ofdefault-metric command as the metric value when distributing other routing protocols.


Table RC-3-14 Specify a Default Route Metric Value for RIP

Operation Command

Specify default route metric value for RIP default-metric metricRestore the default route metric value for RIP no default-metric

By default, the default route metric for RIP is 16.

Since the route metric of route redistribution is changeless, the dynamic routeinformation may be distorted largely. Therefore, routes redistribution cautiously toprevent loss of RIP protocol’s performance.

3.2.15 Specify Additional Route Metric Value for RIP

The additional routing metric here means to add input or output metric for routesobtained via RIP. This does not directly change the route metric value in the routingtable, but will add a designated metric value while receiving or sending routes on theinterface.


Table RC-3-15 Specify additional route metric value for RIP

Operation Command

Specify additional route metric value received for RIP ip rip metricin valueRestore the additional route metric value received for RIP to its default value no ip rip metricinSpecify additional route metric value being advertised for RIP ip rip metricout valueRestore the additional route metric value being advertised for RIP to its defaultvalue no ip rip metricout

By default, additional route metric value received for RIP is 0, ranging from 0 to 16.Additional route metric value being advertised for RIP is 1, ranging from 1 to 16.

3.2.16 Set Route Preference

Each routing protocol has its own preference, deciding which routing protocol will beused to select the best route by IP route strategy. The greater the value is, the lower thepreference will be. RIP preference can be set manually.




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Table RC-3-16 Set route preference

Operation Command

Set the RIP route preference preference valueRestore the default value of RIP route preference no preference

By default, the RIP route preference is 100.

3.2.17 Configure Route Distribution for RIP


1) Configure filtering route information received by RIP.

Table RC-3-17 Filter route information received by RIP

Operation Command

Filter routing information received from a specifiedgateway distribute-list gateway prefix-list-name in

Change or cancel filtering the routing informationreceived from a specified gateway no distribute-list gateway prefix-list-name in

Filter the routing information received distribute-list {access-list-number | prefix-list prefix-list-name } in

Change or cancel filtering routing information received no distribute-list {access-list-number | prefix-listprefix-list-name } in

2) Configure filtering the routing information being advertised

Table RC-3-19 Filter route information being advertised by RIP

Operation Command

Filter the routing information being advertised. distribute-list { access-list-number | prefix-list prefix-list-name } out [ protocol ]

Change or cancel filtering the routing informationbeing advertised

no distribute-list { access-list-number | prefix-list prefix-list-name } out [ protocol ]

By default, RIP does not filter any route information received or being advertised.

protocol specifies the routing domain that can will be filtered. At present, igrp can filterroutes domain such as connected, static, igrp, eigrp, ospf, ospf-ase and bgp.

Please refer to “Configure Route Filter” of “Configure IP routing Protocol-IndependentFeatures” for details.

3.2.18 Reset RIP

VRP1.4 provides RIP system configuration resetting function. When reconfiguring RIPparameters, use this command to restore to the default RIP configuration.




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Table RC-3-19 Reset RIP

Operation Command

Reset RIP reset

3.3 Monitoring and Maintenance of RIP

Table RC-3-20 Monitoring and maintenance of RIP

Operation Command

Show current RIP running status and global configuration information. show ip ripShow all routing information read by RIP show ip rip routeShow snapshot configuration and the running status. show ip rip snapshotTurn on RIP debugging information debug ip rip { recv | send }

1) Show current RIP running status and global configuration information.

Quidway#show IP rip

rip is turning on

checkzero is on default-metric : 16

neighbor: 202.38.165.1

auto-summary is on preference : 100

The above information indicates that RIP is in running status and is operating zero fieldcheck. The default routing metric is 16. unicasting is not specified; RIP preference is100.Note that if unicast has been specified, the corresponding display will be:

neighbor :202.38.165.1

2) Show snapshot configuration and the running status.

Quidway# show IP rip snapshot

Interface Serial 0: snapshot client

Length of Active period: 5 minutes

Length of Quiet period : 10 minutes

Length of Retry period : 8 minutes

Current status : Active , remain 3 minutes

The above information indicates that the active period interval of serial port 0 is 5minutes, quiet period interval is 10 minutes and resending period interval is 8 minutes.The current status is active and there is still 3 minutes before timeout.



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3.4 Typical Configuration of RIP

3.4.1 Configuring RIP Unicast


RIP is a broadcast protocol. It can only exchange routing information with non-broadcasting networks in unicast mode. This example shows how to configure RIPmessage unicasting.

Routers A, B and C are connected in an Ethernet. Router A (192.1.1.1) Ethernetinterface is set to passive interface. Router A only wants to send the routing updatinginformation to the adjacent Router B (192.1.1.2) without sending to Router C(192.1.1.3).


RouterA

RouterB

RouterC

Router A unicasts route updatinginformation to Router B

e0 192.1.1.1

e0 192.1.1.3 e0 192.1.1.2

Figure RC-3-2 Networking diagram of configuring RIP unicast


Configure Router A:

1) Configure serial port 0

RouterA(config)#interface serial 0

RouterA(config-if-serail0)# IP address 192.1.1.1 255.255.255.0

2) Configure RIP

RouterA (config) router rip

RouterA (config-router-rip)#network 192.1.1.0

3) Configure Router A unicast neighbor to be Router B.

RouterA(config-router-rip)# neighbor 192.1.1.2



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3.4.2 Disabling RIP Split-Horizon

I.Networking requirements

This is a typical example that split-horizon can not be used (no IP rip split).

In the diagram, router C connects two sub-networks (frame relay networks) via a serialport. The Ethernet interfaces of routers A, B, and C (connected respectively to network10.24.40.0, 129.102.0.0 and 202.38.165.0) are split-horizontally by default. The threerouters are connected together via a frame relay network. Serial ports of networks131.109.1.0 and 129.125.1.0 also use split-horizon by default.

In this example, split-horizon must be disabled (no IP rip split) on the three routers'serial ports connecting the frame relay network, so that the routes from the network129.125.1.0 can be broadcast to the network 131.109.1.0, and vice versa. These twosub-networks are connected together via serial port 0 of router C. If split-horizon ismade on serial port 0, then the routes of these two sub-networks will not be broadcastback to the frame relay network.

II.Networking diagram

Ethernet

Router

A

Router

B

Router

C

Frame relay networkNetwork Address10.24.40.0

129.102.0.0

202.28.165.0

10.24.40 .1

129.102.0.1202.38.16 5.1

Network Address

129.125.1.0Network Address

131.109.1.0Network Address

Network Address

Interface Address

Interface AddressInterface Address

Figure RC-3-3 Networking diagram of disabling RIP split-horizon

III.Configuration procedure

1) Configure Router A:

! Configure interface Ethernet 0

RouterA(config)# interface ethernet 0

RouterA(config-if-Ethernet0)# ip address 10.24.40.1 255.255.255.0

! Configure interface Serial 1



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(Make sure the link layer works normally before the following configuration.

Please refer to “Frame Relay Configuration” in “WAN Configuration Part” for

the details of frame relay configuration).


RouterA(config-if-Serial1)# ip

address 131.109.1.2 255.255.255.0

RouterA(config-if-Serial1)# encapsulation frame-relay

! Configure RIP

RouterA(config)# router rip

RouterA(config-router-rip)# network 10.24.40.0


2) Configure Route B:


RouterB(config)# interface ethernet 0

RouterB(config-if-Ethernet0)# ip address 202.38.165.1 255.255.255.0


RouterB(config)# interface serial 1

RouterB(config-if-Serial1)# ip address 129.125.1.2 255.255.255.0

RouterB(config-if-Serial1)# encapsulation frame-relay

! Configure RIP

RouterB(config)router rip

RouterB(config-router-rip)# network 202.38.165.0


3) Configure Router C:


RouterC(config)# interface ethernet 0

RouterC(config-if-Ethernet0)# ip address 129.102.0.1 255.255.0.0


RouterC(config)# interface serial 1

RouterC(config-if-Serial1)# ip address 129.125.1.1 255.255.255.0

RouterC(config-if-Serial1)# ip address 131.109.1.1 255.255.255.0 secondary

RouterC(config-if-Serial1)# encapsulation frame-relay

RouterC(config-if-Serial1)# no ip rip split

! Configure RIP

RouterC(config)# router rip



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RouterC(config-router-rip)# network 129.125.1.0

RouterC(config-router-rip)# network 131.109.1.0

3.5 Troubleshooting of RIP

Fault 1: no updating messages can be received when physical connection works well.

Troubleshooting: This may be caused by the following:

l RIP is not running on corresponding interface (maybe no ip rip work command

has been executed), or this interface is not enabled with network command.

Multicasting has been configured on the opposite router (perhaps ip rip version 2

mcast command has been executed), but not configured on the local router.


Chapter 4Configuration of IGRP

4-1

Chapter 4 Configuration of IGRP

4.1 Description of IGRP

Interior Gateway Routing Protocol (IGRP) is also a dynamic D-V algorithm basedrouting protocol. It sets up its routing table by exchanging routing information with itsneighboring routers. IGRP was developed from RIP, and there is IGRP version 1 atpresent.

In comparison with RIP, the following improvement has been made in IGRP:

Improvement on the range and calculation of Metric value: metric contents includereference values such as maximum transmission unit (MTU), interface bandwidth,interface load, interface delay and reliability of interface transmission. A final value iscalculated with a reasonable formula. The maximum of metric is 224, so IGRP is morecompetent than RIP for large-scale network.

Triggered updates, route holddown, split-horizon, and poison-reverse are introduced,so that IGRP can converge quickly when the topology is changed.

IGRP supports multi-route. IGRP support more than one route existing in route table. InRIP, different routes with the same destination and metric will be processed in First-Comer-Priority principle. The route retained finally is that obtained first.

IGRP is also a broadcasting protocol, by which messages are still transmitted inbroadcasting mode. But it does not support multicasting mode.

IGRP also supports multi-autonomous system (AS), i.e. one router can participate inmultiple ASs.

4.2 Configuring IGRP

4.2.1 IGRP Configuration Task List

You have to first enable IGRP routing process to enter IGRP protocol configurationmode, then configure parameters related to IGRP protocol, while for the interface-related parameters, will not subject to whether a IGRP routing process has beenenabled.

IGRP configuration tasks are listed as follows:

l Enable IGRP Routing Process

l Associate a Network with a IGRP Routing Processl Specify the Current IGRP AS Number

l Define a Neighboring Router

l Specify the Status of an Interface

l Specify IGRP Route Metric Weights

l S Specify the Maximum Route Hop Count



4-2

l Disable Route Holddown

l Disable Host Routes

l Enable Split-Horizon Mechanism

l Enable Snapshot

l Configure Route Redistribution for RIPl Specify Default Route Metric Value for IGRP

l Specify Additional Route Metric Value for IGRP

l Specify IGRP Preference

l Configure Route Distribution for IGRP

l Reset IGRP

4.2.2 Enable IGRP Routing Process


Table RC-4-1 Enable IGRP routing process

Operation Command

Enable a IGRP routing process and enter into the IGRP protocol configuration mode. router igrpTurn off a IGRP routing process no router igrp

IGRP routing process is not enabled by default.

The parameters related to an interface will be also invalid after a IGRP routing processis turned off.

4.2.3 Associate a network with a IGRP routing process

To flexibly control IGRP operation, you can configure the corresponding networksegment to IGRP network so that IGRP packets can be received and transmittedthrough the specified interface.

Perform the following task in IGRP protocol configuration mode.

Table RC-4-2 Associate a network with a IGRP routing process

Operation Command

Specify a lists of networks associated with a IGRP routing process network {network-number | all }Delete a lists of networks associated with a IGRP routing process no network {network-number | all }

No network is associated with IGRP routing process by default after IGRP routingprocess is enabled.

After enable a IGRP routing process, you should specify a lists of networks with theIGRP routing process, since IGRP only works on the interface of specified networksegment. IGRP won’t receive or forward route on interfaces of non-specified networksegments, as if these interfaces did not exist. network-number is the address of theenabled or disabled network or it can be the network address of the interfaces.



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When network command is used to a specified address, the interface of the networksegment of this address will be enabled. For example: network 129.102.1.1, use eithershow running-config or show ip igrp command, you can see network 129.102.0.0.

4.2.4 Configure the Current IGRP AS Number




4-4

Table RC-4-3 Configure the current IGRP AS number

Operation Command

Configure the current IGRP AS number asystem as-numberRestore the Current IGRP AS Number to it default value no asystem

The current IGRP AS number is 1 by default.

The number of autonomous system does not need to be registered, so the user canspecify any number for a AS.

4.2.5 Define a Neighboring Router

IGRP is a broadcast protocol. It can only exchange routing information with non-broadcasting networks in unicast mode.


Table RC-4-4 Define a neighboring router

Operation Command

Define a neighboring router with which to exchange routing information neighbor ip-addressRemove a neighboring router with which to exchange routing information no neighbor ip-address

By default, no neighboring routers are defined.

Normally, this command is not recommended because the opposite side does not wishto receive two identical packets at the same time. Also note that when a neighbor sendsmessages, it is equally restricted by such commands as IP igrp work, IP igrp out, IPigrp in and network.

4.2.6 Specify the Status of an Interface

You can specify the working status of IGRP on the interface in interface configurationmode, such as whether IGRP should be run on the interface, i.e. whether IGRPrefreshed messages should be transmitted and received on the interface. You can alsospecify separately whether updated messages should be transmitted or received onthe interface.


Table RC-4-5 Specify the status of an interface

Operation Command

Specify the Autonomous System number supported by an interface ip igrp asystem as-number [ as-number ][ as-number ] [ as-number ] [ as-numbe ]

Restore the default IGRP Autonomous System on the interface ip igrp workDisable running IGRP on the interface no ip igrp workSpecify receiving IGRP update packets on the interface ip igrp inputDisable receiving IGRP update packets on the interface no ip igrp inputSpecify sending IGRP update packets on the interface ip igrp outputDisable transmitting IGRP updated packets on the interface no ip igrp output



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By default, an interface can both receive and send IGRP update packets.

The IP igrp asystem command can be used to make IGRP support multipleautonomous systems at different interfaces. By default, each interface will only supportthe autonomous system set by the asystem command. When this command is used ona certain interface, this interface can simultaneously support the multiple autonomoussystems set by this command. One interface can participate in 5 autonomous systemsat most.

Here the no ip igrp work command is similar to the no network command in that theinterface using either command no longer tranceives IGRP route. And they differ in thatin the no ip igrp work mode, routes of related interfaces are forwarded, while in the nonetwork mode, routes of related interfaces are not forwarded as if an interface wasmissing.

In addition, ip igrp work functions in equivalence to the combination of two commandsip igrp input and ip igrp output.

4.2.7 Specify IGRP Metric Weights

An outstanding feature of IGRP is metric presentation. The metric in IGRP protocol is acomprehensive metric, which uses a certain algorithm to integrate the topological delay,bandwidth, path load and reliability into a combined metric. K1, K2, K3, K4, K5 and tosare constants in such calculation. The greater the k value, the greater the weight ofcharacteristic volume related to k in the routing metric. If the k is zero, it means that thischaracteristic value is not considered in the integrated routing metric. You can changethe weights to make these calculated metric values more suitable to some specialcases. However, the change of these weights may greatly change the calculation resultof the metric, so the configuration must be done under the guide of professionals.

IGRP metric calculation formula:

metric = [(K1 * bandwidth) + (K2 * bandwidth) / (256 - load ) +( K3 * delay)] *[K5/(reliability + K4)]

If K5 is 0, there will be no Reliability item in the formula, which will be changed to:

metric = (K1 * bandwidth) + (K2 * bandwidth) / (256 - load ) + (K3 * delay)

The formula shows that IGRP metric parameters include bandwidth, load, delay andreliability, which associate metric with all factors affecting data transmission, so as toexactly reflect the quality of the route. But the route is considered not reachable whenMTU is less than 1 or Hopcounts is more than 255.

Here, delay = delay in message + delay on corresponding interface

bandwidth = MAX (bandwidth in message and bandwidth on the interface)

reliability = MIN (reliability in message and that on the interface)

load = MAX (load in the message and that on the interface)

Hopcounts = Hopcounts in the message + 1

MTU = MAX (MTU in message and that on the interface)




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Table RC-4-6 Specify IGRP metric weights

Operation Command

Specify IGRP metric weights metric weights tos k1 k2 k3 k4 k5Restore the IGRP metric weights to their default value no metric weights

k1, k2, k3, k4 and k5 are coefficients for calculating bandwidth, loading, delay andreliability respectively. tos is the Type of Service (at present only service 0 issupported).

By default, tos=0, k1=k3=1, k2=k4=k5=0.

4.2.8 Specify the Maximum Route Hop Count

Route metric in IGRP is a 24bits number. If a loop occurs, the convergence will be veryslow. Setting maximum hop count in IGRP is a security mechanism to prevent loop. Aroute with its hop count larger than maximum hop count will be regarded asunreachable.


Table RC-4-7 Specify the maximum route hop count

Operation Command

Specify the maximum route hop count for IGRP metric maximum-hops hopsRestore the maximum route hop count for IGRP to its default value no metric maximum-hops

By default, the maximum route hop count for IGRP is 100.

4.2.9 Disable Route Holddown

Route holddown is a strategy adopted in IGRP protocol to prevent loops. When a routeget unreachable, the route enters holddown period, during which this route is sent asunreachable and any reachable information of this route will be ignored. It is at the costof efficiency. In route holddown period, the unreachable or timeout route is deleted fromthe routing table directly


Table RC-4-8 Disable route holddown

Operation Command

Disable route holddown no metric holddownEnable route holddown metric holddown

By default, route holddown is enabled.



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4.2.10 Disable Host Routes

In some special cases, the router may receive large number of host routes from thesame network segment. These routes occupy lots of network resources and are of lessuse in route addressing. You can configure disable host route function to reject thesehost routes.


Table RC-4-9 Disable host routes

Operation Command

Disable Host Routes no host-routeEnable Host Routes host-route

By default, the router enables to receives host routes.

4.2.11 Enable Split-Horizon

IGRP is also a D-V algorithm based routing protocol, using split-horizon to preventroute loop. But in some special circumstances, split-horizon shall be disabled,sacrificing efficiency for good transmission quality. It is recommended not to disable theIGRP split-horizon unless necessary. For point-to-point connected links, disablingsplit-horizon is not effective.


Table RC-4-10 Enable split-horizon

Operation Command

Enable split-horizon mechanism on the interface ip igrp splitDisable split-horizon mechanism on the interface no ip igrp split

By default, split-horizon mechanism is enabled on an interface.

4.2.12 Enable Snapshot

I. Working principle of snapshot

The snapshot function of IGRP has improved on bandwidth seizure and overheadcaused by periodic forwarding of D-V protocol. It is mainly used in Dial-On-Demandnetwork. Refer to relevant parts in “Chapter 3 RIP Protocol Configuration” for thedetails.

II. Configure snapshot at client

Two time segments should be configured. One is the active-interval, and the otherquiet-interval.




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Table RC-4-11 Enable snapshot

Operation Command

Specify the duration of active interval and quiet interval at server ip igrp snapshot client active-interval quiet-interval

Delete the duration of active interval and quiet interval at server no ip igrp snapshot client

The duration of active-interval should be at least 3 minutes longer than that of quiet-interval.

III. Configure snapshot at server

At snapshot server, only an active period should be configured. The client determinesother time segments. Please note that the active period at the server should be thesame as that at the client during configuration.


Table RC-4-12 Configure snapshot at server

Operation Command

Specify the duration of active interval and quiet interval at client ip igrp snapshot server active-intervalDelete the duration of active interval and quiet interval at client no ip igrp snapshot server

By default, snapshot is disabled on the interface.

4.2.13 Configure Route Redistribution for IGRP

IGRP permits the user to redistribute the routes from other domain into the routing table


Table RC-4-13 Filter route information received by RIP

Operation Command

Configure route redistribution for IGRP redistribute protocol [ metric metric ] [ route-map map-name ]Cancel route distribution for IGRP no redistribute protocol

By default, IGRP does not redistribute routes from other domain into the routing table.

protocol specifies the source routing domain that can be redistributed. At present, igrpcan redistribute routes domain such as connected, static, rip, eigrp, ospf, ospf-ase andbgp.


4.2.14 Specify Default Route Metric Value for IGRP

By default, IGRP does not broadcast the routes of other protocols, but can redistributeroutes of other routing protocols by running the redistribute command. When runningredistribute command, if no metric parameters have been specified in the command,



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the related parameters in the default-metric command will be used as the metricparameters for redistribute.




4-10

Table RC-4-14 Specify default route metric value for IGRP

Operation Command

Specify default route metric value for IGRP default-metric bandwidth delay reliability loading mtuRestore the default route metric value for IGRP no default-metric

By default, bandwidth=166777215, delay=166777215, reliability=loading=255, mtu=1.

Since the metric of the redistributed route is fixed, which may cause distortion of thedynamic routing information. Therefore routes should be redistributed with caution sothat the performance of the local route will not be lowered due to the redistributedroutes.


Each routing protocol has its own preference, which decides the route obtained by therouting protocol that will be used as the best route by IP route strategy. The greater thepreference value, the lower the preference. The protocol preference can be configuredmanually.


Table RC-4-15 Set IGRP route preference

Operation Command

Set IGRP route preference preference valueRestore the default value of IGRP route preference no preference

By default, the IGRP route preference is 80.

4.2.16 Configure Route Filter for IGRP


1) Configure filtering routes received by IGRP.

Table RC-4-16 Configure filtering routes received by IGRP

Operation Command

Filter route information received from a specifiedgateway distribute-list gateway prefix-list-name in

Change or cancel filtering the route informationreceived from a specified gateway no distribute-list gateway prefix-list-name in

Filter the route information received distribute-list { access-list-number | prefix-list prefix-list-name } in

Change or cancel filtering route informationreceived

no distribute-list { access-list-number | prefix-list prefix-list-name } in

2) Configure filtering routes being advertised by IGRP.



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Table RC-4-17 Configure filtering routes being advertised by IGRP

Operation Command

Filter the route information being advertised distribute-list { access-list-number | prefix-listprefix-list-name } out [ protocol ]

Change or cancel routing information being advertised no distribute-list { access-list-number | prefix-listprefix-list-name } out [ protocol ]

By default, IGRP does not filter any route information received or being advertised.

protocol specifies the routing domain that can will be filtered. At present, igrp can filterroutes domain such as connected, static, rip, eigrp, ospf, ospf-ase and bgp.


4.2.17 Reset IGRP

When reconfiguring IGRP parameters, use this command to restore to the defaultIGRP configuration.


Table RC-4-18 Reset IGRP

Operation Command

Reset IGRP reset

4.3 Monitoring and Maintenance of IGRP

Table RC-4-19 Monitoring and maintenance of IGRP

Operation Command

Show current IGRP running status and global configurationparameters. show ip igrp

Show all routing read by IGRP show ip igrp routeShow snapshot configuration and the running status. show ip igrp snapshotTurn on IGRP debugging information debug ip igrp { recv | send }

1) Show IGRP running status and its configuration information.

Quidway(config)# show ip igrp

Igrp is turning on

asystem number 1

metric holddown is on

metric max-hops 100

metric weights TOS:0 K1:1 K2:0 K3:1 K4:0 K5:0

default-metric



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bandwidth:0 delay:16777215 reliability:255 loading: 255 mtu:1

no neighbor

no network all

preference 80

show ip igrp is used to show current IGRP running status and global configurationinformation. Note that this command does not show some default configurations.

2) Show snapshot configuration and the running status.

Quidway# show ip igrp snapshot

Interface Serial 0 snapshot client

Length of Active period : 5 minutes

Length of Quiet period : 10 minutes

Length of Retry period: 8 minutes

Current status : Active , remain 3 minutes

The above information indicates that the active period interval of serial 0 is 5 minutes,quiet period interval is 10 minutes and resending period interval is 8 minutes. Thecurrent status is active and it is timeout in 3 minutes.

4.4 Typical Configuration of IGRP

4.4.1 Configure Default Metric for IGRP Routes Redistribution


In the diagram below, WAN1 uses the OSPF routing protocol, while WAN2 uses theIGRP protocol. Normally, the route between WAN1 and WAN2 can not beinterconnected. But WAN2 can obtain the route of WAN1 with the IGRP routeredistributing function.


Route

r

WAN1(OSPF)

WAN2(IGRP)

Serial1 address202.38.169.1(OSPF)

202.38.160.1(IGRP)

Serial2 address

Figure RC-4-1 Networking diagram of configuring default metric of IGRP redistributed routes


Configure Router:

1) Enable IGRP routing process

Quidway (config)# router igrp



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2) Configure default metric of IGRP redistributed routes

Quidway (config-router-igrp)# default-metric 1000 100 250 100 1500

3) Redistribute routes discovered by OSPF protocols.

Quidway (config-router-igrp)# redistribute ospf

Here default-metric means: path bandwidth is 1000kbps, topological delay is 1000ms,path reliability is 98%, path channel seizure rate is 39%, and maximum transmissionunit is 1500 bytes.

4.5 Troubleshooting of IGRP

Fault 1: IGRP does not work normally after startup.

Troubleshooting: perform the following procedures:

l IGRP protocol is the IP-layer routing protocol. You should be able to ping throughthe interface running IGRP protocol and the opposite interface, so that IGRP on

this interface can work normally.

l IGRP protocol sends messages in the broadcast mode. So when the lower layer

encapsulates X.25 (or similar link layer protocol such as frame relay), the map of

the lower layer protocol should be configured into the broadcast-supported mode(refer to corresponding position) to transmit broadcast messages. If broadcast is

not supported, the opposite side should be specified as neighbor.

Example: while configuring X.25 mapping on serial 0, the IP address and X.121address of the opposite side are respectively 202.38.161.1 and 100, then theconfiguration shall be:

Quidway (config-if-Serial0)#x25 map IP 202.38.161.1 100 broadcast


Chapter 5 Configuration of EIGRP

5-1


5.1 Brief Introduction of EIGRP

EIGRP is enhanced IGRP protocol, still using D-V algorithm, but its convergencecharacteristics and operation efficiently is much better than those of IGRP.

EIGRP features the following:

l Multiple routing process: multiple EIGRP routing processes can run on one router

at the same time and they are distinguished by Autonomous System number.

Different processes do not interfere with each other and they can redistribute

routes to each other.l Fast convergence and loop-free: the received routing information is processed

with Diffusing Update Algorithm (DUAL), generating the shortest routing

information to the destination networks. When there is change on the network, the

route will be recalculated. EIGRP route calculation involves only the necessary

routes and routers, rather than the whole network. The convergence time ofEIGRP excels any other existing routing protocols.

l Partially update: neighboring routers exchanges routing information only when the

route changes and only the changed routing information is switched, thus less

bandwidth is seized by EIGRP protocol.

l Neighbor discovery: Routers also must discover when their neighbors becomeunreachable or inoperative. This process is achieved with low overhead by

periodically sending small hello packets. As long as a router receives hello

packets from a neighboring router, it assumes that the neighbor is functioning, and

the two can exchange routing information.

l Support variable length sub-net mask.l Random route convergence: After route convergence, only one routing

information in the convergence area is transmitted, thus less network bandwidth,

less processor & memory resources are seized.

l Applicable for larger network: EIGRP routing metric is calculated with parameters

such as network delay, bandwidth and effective bandwidth. It is a number of 32bits. EIGRP metric value indicates the status of network link accurately and makes

IEGRP applicable to large area network.

l Route redistribution: static routes, other protocol routes or the routes found by

other EIGRP processes can be redistributed. When IGRP and EIGRP routes are

redistributed, directly use the original metric value of IGRP and EIGRP. Whenother protocol routes are redistributed, use the metric value of the specified

routes.



5-2

EIGRP protocols are implemented with the following mechanisms:

l Neighbor discovery and maintenance

l Topology table maintenance

l DUAL finite state machinel Message organization and reliable transmission

Neighbor discovery is implemented by EIGRP sending low-overhead hello packet onthe interfaces with multicasting (224.0.0.10) regularly. The router receiving the hellopacket will this router into its “Neighbor Table”, then this two routers start exchangingrouting information. Later on, every time when hello packet is received, the router willregard the opposite route as “Live” and exchange information with. If hello packet is notreceived from the opposite router for a certain time, the opposite router will beconsidered dead and deleted from the neighbor table, with all routers informed that thisrouter is unreachable. In this way EIGRP can respond to the network change quickly.

If two routers are neighbors, they will exchange all routing information for the first time.Then only when the network structure or route changes will the change be advertised.EIGRP has not a regular route updating mechanism of RIP.EIGRP saves all receivedrouting information including destination address of route, mask, next hop and metric ina “Topology Table”. Use DUAL to select the best route without loop and add to therouting table.

DUAL is the core of EIGRP. It ensures that there is no loop with EIGRP protocolcalculation. DUAL finite state machine is used to describe the processing of all routecalculation. The finite state machine ensures that DUAL can be converged. DUALselects the effective path without loop with metric information. DUAL is also a D-Valgorithm. The basic principle of DUAL: to find the distance from a router to adestination network, add the distance from the router to its neighbor and that from theneighbor to the destination network. The sum of the two is the distance from the routerto the destination network via this neighbor. Then calculate the metric of all neighborsand select the minimum value. This is the shortest distance from the router to thedestination network. DUAL selects the best route from the feasible successor andinserts it into the routing table. A feasible successor is a neighboring router used forpacket forwarding that is a least-cost path to a destination that is guaranteed not to bepart of a routing loop. When a route has no feasible successor, and a neighbor routerannounces that it can access this destination, route recomputation becomes necessary.It is also a process to re-define a feasible successor.

On the network change, DUAL will first test whether there is a feasible successor forthe destination network.

1) If yes, the best feasible successor will be singled out as the next hop to the

destination network and there is no need for route recomputation.

2) If there is no feasible successor and there is no route item about this destination

address in the Topology Table, it means that the destination network becomesunreachable.

3) If there is no feasible successor while there is route item to this destination in the

topology table, the route reported by this neighboring router can not meet the

requirement of feasible successor and loop-free cannot be guaranteed. In such

case, this neighboring router can not be used as the next hop to the destinationand DUAL will be started again to recompute routes, i.e. re-define a feasible

successor. Recomputation does affect convergence time, so it is advantageous to

avoid unnecessary recomputations.



5-3

In the above computation, packets are transmitted between neighboring routers. Thesepackets carry EIGRP routing information. EIGRP transmits packets betweenneighboring routers with Raw IP. As Raw IP is unreliable, EIGRP must setup a reliabletransmission system of its own. EIGRP ensure reliable message delivery with S/Nconfirmation and timeout resending mechanism. Reliable transmission is veryimportant for EIGRP because it ensures that EIGRP packets are sent to all neighbors.Reliable transmission is not always required and it is used when necessary as it affectsthe transmission efficiency.

5.2 Configuring EIGRP

5.2.1 EIGRP Configuration Task List

You have to first enable EIGRP routing process to enter EIGRP protocol configurationmode, then configure parameters related to EIGRP protocol, while for the interface-related parameters, will not subject to whether a EIGRP routing process has beenenabled.

EIGRP configuration tasks are listed as follows:

l Enable EIGRP Routing Process

l Associate a Network with a EIGRP Routing Process

l Configure a Passive Interface

l Configuring EIGRP link bandwidth availabilityl Configuring EIGRP metric weights

l Configuring EIGRP Offset-list

l Enable Auto Summary

l Configuring route summary of any mask length

l Message authenticationl Configuring hello packet sending interval and neighbor breakdown time

l Enable split-horizon

l Configure Route Redistribution for EIGRP

l Setting the original metric of redistributed routes

l Specify Default Route Metric Value for EIGRPl Set EIGRP preference

l Configure Route Redistribution for EIGRP

5.2.2 Enable EIGRP Routing Process


Table RC-5-1 Enable EIGRP routing process

Operation Command

Enable a EIGRP routing process and enter into the EIGRPprotocol configuration mode router eigrp as-number

Turn off a EIGRP routing process no router eigrp as-number



5-4

EIGRP routing protocol supports multiple routing process. Multiple EIGRP routingprocesses can be enabled at the same time with the AS number as the ID. MultipleEIGRP routing processes can run independently.

EIGRP routing process is not enabled by default.

5.2.3 Associate a Network with a EIGRP Routing Process

To control EIGRP operation freely, you can configure the corresponding networksegment to EIGRP network so as to receive and transmit EIGRP messages throughthe specified interface.

Perform the following task in EIGRP protocol configuration mode.

Table RC-5-2 Associate a Network with a EIGRP routing process

Operation Command

Specify a lists of networks associated with a EIGRP routing process network network-numberDelete a lists of networks associated with a EIGRP routing process no network network-number

EIGRP routing process is disabled on all interfaces by default.

After enable an EIGRP routing process, you should specify a lists of networks with theEIGRP routing process, since EIGRP only works on the interface of specified networksegment. EIGRP won’t receive or forward route on interfaces of non-specified networksegments, as if these interfaces did not exist. network-number is the address of theenabled or disabled network or it can be the network address of the interfaces.

5.2.4 Configure a Passive Interface

To prevent EIGRP routing information from being obtained by the router domain, usepassive-interface command to disable EIGRP packets to be received and sent on aspecified interface.


Table RC-5-3 Configure a passive interface

Operation Command

Configure a passive interface passive-interface interface-type interface-number

Delete a passive specified interface no passive-interface interface-type interface-number

EIGRP packets can be received and sent on all interfaces by default.

passive-interface command and no network command differ in that the former onlyrestricts EIGRP messages receiving and transmitting on the interface and the interfaceroutes can still be transmitted through other interfaces, while if the later is used, EIGRPmessages are not sent on this interface nor will the interface routes be transmittedthrough other interfaces.



5-5

5.2.5 Configure the Percentage of Bandwith Used by EIGRP

EIGRP provides bandwidth-percent configuration command to modify link bandwidthoccupation, so that the maximum occupied bandwidth on the link will not exceed theconfigured range, which may result in the failure of data & message transmission dueto bandwidth shortage.




5-6

Table RC-5-4 Configure the percentage of bandwith used by EIGRP

Operation Command

Configure the percentage of bandwith that may be usedby EIGRP on an interface ip bandwidth-percent eigrp as-number percent

Restore the percentage of bandwith that may be used byEIGRP on an interface to its default value no ip bandwidth-percent eigrp as-number

By default, the percentage of bandwith that may be used by EIGRP on an interface is50%.

The percentage of Bandwith used by EIGRP on an interface means the maximum linkbandwidth allowed when EIGRP sends packets. But that does not means that EIGRPcan process such a percentage of bandwidth all along.

5.2.6 Configure EIGRP Metric Weights

The metric in the EIGRP protocol is a comprehensive metric, which uses a certainalgorithm to integrate the topological delay, bandwidth, path load and reliability into acombined metric. K1, K2, K3, K4 and K5 are system constants. You can change theweights, so that the calculated metric values will be more suitable to some specialcases. However, this operations may greatly change the metric value and shall be doneunder the guide of professionals.


Table RC-5-5 Configure EIGRP metric weights

Operation Command

Configure EIGRP metric weights metric weights tos k1 k2 k3 k4 k5Restore default value of EIGRP routing metric weights no metric weights

k1, k2, k3, k4 and k5 are coefficients for calculating bandwidth, loading, delay andreliability respectively. tos is the Type of Service (at present only service 0 issupported).

By default, tos=0, k1=k3=1, k2=k4=k5=0.

Please note that the five k values must be consistent between EIGRP neighbors,otherwise the neighboring relation can not be established.

5.2.7 Configure an Offset-list

The offset-list can be matched with access control list. If successful, an offset-list will beadded to the route delay. If interface using increment list is configured, the incrementlist will be used only on the specified interface, otherwise it will be used on allinterfaces.




5-7

Table RC-5-6 Configure an offset-list

Operation Command

Apply an offset-list to routing metrics offset-list access-list-number { in|out } offset [ interface-type interface-number ]

Remove an offset-list no offset-list access-list-number { in |out } offset [ interface-typeinterface-number ]

EIGRP does not apply an offset-list to routing metrics by default.

5.2.8 Enable Route Automatic Summarization

EIGRP auto summary function summarizes the subnet route into the route of naturalnetwork segment. The auto summary function works only when two or more networksare configured in EIGRP process.

EIGRP supports two kinds of route summaries: automatic summary and variable lengthmask summary. EIGRP auto summary is enabled by default. The summary area is allnatural network segments. Variable length mask summary can be configured on theinterface as necessary. The summary range is specified by the configured networksegment address and mask.

The two types of route summaries differ in configuration and similar in processing. Afterroute summery configuration, a summary route will be generated out of all routes in therange. The metric value of this route is the minimum value in the summary range. Whenmessages are transmitted externally, EIGRP only sends this summary route as therepresentative of other routes, while other route beyond the summary range will not bedistributed. The receiving router processes the route in the same way as it processesother routes. Summary route can reduce the network bandwidth occupied by packets,reduce the memory consumed by saving routing information and lower the load of CUPon the router.


Table RC-5-7 Enable route automatic summarization

Operation Command

Disable route automatic summarization no auto-summaryEnable route automatic summarization auto-summary

By default, route automatic summarization is enabled in EIGRP.

5.2.9 Enable Route Summarization of any Length Mask

EIGRP can summarizes routes of any mask length sent by the interface.


Table RC-5-8 Enable route summarization of any length mask

Operation Command

Enable route summarization of any length mask ip summary-address eigrp as-number address mask



5-8

Delete route summarization of any length mask no ip summary-address eigrp as-number address mask

By default, route summarization of any length mask is disabled.

5.2.10 Configure Authentication for EIGRP

EIGRP only provides MD5 authentication to messages. Messages failed to pass theauthentication will be discarded.

Key-id should be specified when MD5 is used in interface (ip authentication key-ideigrp as-number key-id). Each key-id identifies current MD5 arithmetic and its key-id.The latter configured key-id will replace the former one.


Table RC-5-9 Configure authentication

Operation Command

Specify a key-id for EIGRP MD5 authentication ip authentication key-id eigrp as-number key-idDelete a key-id for EIGRP MD5 authentication no ip authentication key-id eigrp as-number

Specify a key-string for EIGRP MD5 authentication ip authentication key-string eigrp as-numberpassword

Delete a key-string for EIGRP MD5 authentication no ip authentication key-string eigrp as-numberEnable MD5 authentication for EIGRP ip authentication mode eigrp as-number md5

Disable MD5 authentication for EIGRP no ip authentication mode eigrp as-numbermd5

By default, no authentication is performed on the interface.

5.2.11 Configure Hello Interval and Hold Time Interval

EIGRP sends Hello packets to the interfaces every 5 seconds by default, which iscontrolled by a Hello Interval timer. When a router receives a Hello packet from anotherrouter, it will perform the following operations:

1) Refuse to process the packet if the AS number and K value are different from its

own.2) Restart the neighbor hold time timer if the neighbor is already in the neighbor table.

The interval of the timer is specified with the hold time parameter in Hello packet. If

no hello packet is received from the neighbor for 15 seconds, this neighbor will be

considered invalid and then deleted from the route table.

3) Add the neighbor to the routing table if it is not there. Start hold time timer. Theinterval of the timer is specified with the hold time parameter in hello packet.


Table RC-5-10 Configure hello interval and hold time interval

Operation Command

Configure hello interval for EIGRP ip hello-interval eigrp as-number secondsRestore default value of hello interval no ip hello-interval eigrp as-numberConfigure hold time interval for EIGRP ip hold-time eigrp as-number secondsConfigure default value of hold time interval no ip hold-time eigrp as-number



5-9

By default, hello interval is 5 seconds and hold time interval is 15 seconds.

5.2.12 Enable Split-Horizon

Split-horizon is only effective in EIGRP route updating messages and query messages.On the interface enabling split-horizon, the transmitted updating message and querymessage do not include the routing information of next hop interface for this interface.This can reduce the chance of loops. But on some NBMA interfaces, since NBMAnetwork is not wholly interconnected, split-horizon may result in loss of some routinginformation. Disable split-horizon on this interface.


Table RC-5-11 Enable split-horizon

Operation Command

Enable split-horizon mechanism on the interface ip split-horizon eigrp as-numberDisable split-horizon mechanism on the interface no ip split-horizon eigrp as-number

By default, split-horizon is enabled on the interface.

5.2.13 Configure Route Redistribution for EIGRP

EIGRP permits the user to redistribute the routing information of other protocols into therouting table.

The metric value of the redistributed route should be calculated as follows:

l Redistribute the route of crossover network and calculate the metric of the

redistributed route according to attributes of the interface where the crossover

network segment is located.

l Redistribute IGRP route and use metric component of IGRP directly.

l Redistribute EIGRP route of other autonomous system and use EIGRP metricdirectly.

l Redistribute other routing protocols (including static route, OSPF, RIP and BGP)

and specify the components (delay, bandwidth) of metric in the command. If the

metric value is specified for the command, calculate with the valued. If it is not

specified, set metric value with default-metric command.


Table RC-5-12 Configure route redistribution for EIGRP

Operation Command

Configure route redistribution for EIGRP redistribute protocol [ metric metric ] [ route-map map-name ]Cancel route distribution for EIGRP no redistribute protocol

By default, EIGRP does not redistribute routes from other domain into the routing table.



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protocol specifies the source routing domain that can be redistributed. At present, igrpcan redistribute routes domain such as connected, static, rip, igrp, ospf, ospf-ase andbgp.


5.2.14 Set Metric Value for EIGRP in a Route-map

When EIGRP is redistributing other routes (such as static route, OSPF, RIP, BGP), youcan specify delay, bandwidth, etc. If set metric value is specified in set metriccommand, calculate with the specified value. Otherwise, calculate with the valuespecified in default-metric command.

Perform the following task in route mirror configuration mode.

Table RC-5-13 Set metric for EIGRP in a route-map

Operation Command

Set metric value for EIGRP in a route-map set metric bandwidth delay reliability loading mtuRestore to the default metric value for EIGRP no set metric

By default, no metric value for EIGRP in a Route-map is set.

5.2.15 Configuring Default Metric of Redistributed Routes

When using redistribute command to redistribute other routing protocols, if no metricparameters have been specified in the command, the related parameters in thedefault-metric command will be used as the parameters for redistribute .


Table RC-5-14 Configure default metric of redistributed routes

Operation Command

Configure default metric of redistributed routes default-metric bandwidth delay reliability loading mtuRestore default value of redistributed route metric. no default-metric

When redistributing direct route or static route is, it is not necessary to set default routemetric

Since the metric of the redistributed route is fixed, which will distort the dynamic routinginformation to a great extent. Therefore routes should be redistributed with caution sothat the performance of the local route will not be lowered due to the redistributedroutes.


EIGRP has two routes: internal routes and external routes, which are redistributed withredistribute command. The preference metric of EIGRP internal routes and externalroutes are different.



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Multiple routing processes may run in one router at the same time. The performance ofvarious routing processes are different, therefore different preferences are set. Thecore routing table will select a best route based on the routing preference.

Perform the following task in EIGRP strategy configuration mode.



5-12


Operation Command

Set EIGRP internal and external route routes distance internal-preference external-preferenceRestore the default preference value of EIGRPinternal and external routes no distance

By default, the preference of EIGRP internal route is 50 and that of the external route is170. The value range of the internal/external preference is 1-255.

5.2.17 Configure Route Filter for EIGRP

In the process of route filtering, EIGRP processes the routing information as follows:

l Filter the received & transmitted messages with distribute-list command, to

disable the transmitting and receiving of some routes.

l Modify the metric value of the received and outbound distributed routes withoffset-list in/out setting, to add an offset to the delay of metric of some routes.

l If horizon split is adopted on the interface, some routing information will be filtered

as required by the horizon split. Refer to “Disabling Split-Horizon” for details.

l If route summary is configured on the interface (including automatic summary and

variable length mask summary), only the generated summary route will be sentand all other routes in the summary area will not be sent.


1) Configure Filtering Route Information Received by EIGRP

Table RC-5-16 Filter route information received by EIGRP

Operation Command

Filter the route information received from a specifiedgateway distribute-list gateway prefix-list-name in

Change or cancel filtering the route information receivedfrom a specified gateway no distribute-list gateway prefix-list-name in

Filter the route information received by EIGRP distribute-list { access-list-number | prefix-listprefix-list-name } in

Change or cancel filtering route information received byEIGRP

no distribute-list { access-list-number | prefix-listprefix-list-name } in

2) Configure Filtering Route Information being Advertised by EIGRP.

Table RC-5-17 Filter route information being advertised by EIGRP

Operation Command

Filter route information being advertised by EIGRP distribute-list { access-list-number | prefix-list prefix-list-name } out [ protocol ]

Change or cancel filtering of routes being advertisedby EIGRP.

no distribute-list { access-list-number | prefix-listprefix-list-name } out [ protocol ]

By default, EIGRP does not filter any route information received or being advertised.



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protocol specifies the routing domain that can will be filtered. At present, eigrp can filterroutes domain such as connected, static, rip, igrp, eigrp, ospf, ospf-ase and bgp.


3) Apply an Offset-list on the Specified Interface

You can match the increment list with the received and transmitted EIGRP routes withaccess-list command. If successful, the metric of the matched routes will be added. Ifinterface is configured, the increment list is only used on specified interface, otherwiseit will be used on all interfaces.

Table RC-5-18 Apply an offset-list on the specified interface

Operation Command

Apply an offset-list on the specified interface offset-list access-list-number { in |out } offset [ type number ]Delete an offset-list on the specified interface no offset-list access-list-number { in |out } offset [ type

number ]

By default, no offset-list is applied on any interface.

5.3 Monitoring and Maintenance of EIGRP

Table RC-5-19 Monitoring and maintenance of EIGRP

Operation Command

Show information of current EIGRP interface show ip eigrp interfaceShow information in current EIGRP neighbor table show ip eigrp neighbor

Show information in current EIGRP topology tableshow ip eigrp topology [ active | all-link |passive | pending | summary | zero-succs ]

Show current EIGRP traffic statistic information. show ip eigrp trafficTurn on EIGRP debugging switch (receiving and transmittingmessage, timer, event and finite state machine)

debug eigrp { event | fsm | neighbors |packets | task | timers | transmit }

Turn on EIGRP debugging switch (notifications, summary) debug ip eigrp [ notifications | summary ]

1) Show information in current EIGRP interface

Quidway# show ip eigrp interfaces

IP-EIGRP Interfaces for process 100

Xmit Queue Mean Pacing Time Multicast Pending

Interface Peers Un/Reliable SRTT Un/Reliable Flow Timer Routes

Serial0 0 0 / 0 0 0 / 10 0 0 0

Ethernet0 0 0 / 0 0 0 / 10 0 0 0

show ip eigrp topology command shows the DUAL status in EIGRP topology table.This command can be used as a quick reference to ensure that ELGRP is configured toa given interface of a specified AS.

2) Show information in current EIGRP neighbor table

Quidway# show ip eigrp neighbors

IP-EIGRP neighbors for process 200



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H Address Interface Hold Uptime SRTT

(sec)

1 192.168.13.3 Ethernet0 15 0: 0:55 1

0 192.168.13.4 Ethernet0 12 0: 4: 9 3683

show ip eigrp interfaces command shows the neighbor information of all currentEIGRP processes.

3) Show information of current EIGRP topology table

Quidway# show IP eigrp topology

IP-EIGRP topology table for process 100

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,

r - Reply status

P 8.0.0.0/8, 1 successors, FD is 40511488 via connected, Serial0

P 192.168.13.0/24,1 successors, FD is 281600 via connected,Ethernet0

show ip eigrp topology command shows the DUAL arithmetic state in ELGRPtopology table. This command is very useful in troubleshooting.

4) Show current EIGRP traffic statistic information.

Quidway# show ip eigrp traffic

IP-EIGRP Traffic Statistics for process 1

Hellos sent/received: 0/0

Updates sent/received: 0/0

Queries sent/received: 0/0

Replies sent/received: 0/0

Acks sent/received: 0/0

IP-EIGRP Traffic Statistics for process 100

Hellos sent/received: 30/0

Updates sent/received: 0/0

Queries sent/received: 0/0

Replies sent/received: 0/0

Acks sent/received: 0/0

show ip eigrp traffic command shows the EIGRP traffic statistic information receivedand transmitted by the router (such as packet types and sequence numbers).

5.4 Typical Configuration of EIGRP

5.4.1 Configure EIGRP Route Authentication

I. Networking requirement

To make sure that the router gets routing information from a reliable neighbor, you canconfigure EIGRP route authentication on the router. In the following networking



5-15

diagram, Quidway refer to Quidway series router of Huawei, and Router refers to Ciscorouter.


V.35/HDLC202.12.2.1/24 129.102.1.1/16 129.102.1.2/16 10.0.0.1/8

s0s0 e0e0Quidway Cisco

Figure RC-5-1 Networking diagram of configuring EIGRP route authentication


1) Configure Quidway router A:


Quidway(config)# interface serial 0

Quidway(config-if-serial0)# ip address 129.120.1.1 255.255.0.0


Quidway(config)# interface ethernet 0

Quidway(config-if-Ethernet0)# ip address 202.12.2.1 255.0.0.0

! Start EIGRP

Quidway(config)# router eigrp 10

Quidway(config-router-eigrp)# network 202.12.2.0

Quidway(config-router-eigrp)# network 129.102.0.0

! Configure authentication on the interface

Quidway(config-if-serial0)# ip authentication mode eigrp 10 md5

Quidway(config-if-serial0)# ip authentication key-string eigrp 10 1234567890

Quidway(config-if-serial0)# ip authentication key-id eigrp 10 1

2) Configure Quidway router B:


Quidway(config)# interface serial 0

Quidway(config-if-serial0)# ip address 129.102.1.2 255.255.0.0



Quidway(config-if-ethernet0)# ip address 10.0.0.1 255.255.255.0

! Enable EIGRP routing process



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Router(config)# router eigrp 20

Router(config-router)# network 129.120.0.0

Router(config-router)# network 10.0.0.0

! Configure authentication on the interface

Quidway(config-if-Serial0)# ip authentication mode eigrp 20 md5

Quidway(config-if-Serial0)# ip authentication key-string eigrp 20 1234567890

Quidway(config-if-Serial0)# ip authentication key-id eigrp 20 1

5.4.2 Configure EIGRP Timers


EIGRP uses Hello packet to discover neighbors and get information about whether theneighbor is unreachable or invalid. By default, the packet is sent every 5 seconds. Thedefault hold time is 3 times of the interval of sending Hello packets. If the routerreceives another hello packet, the neighbor will be deleted from the neighbor list.


Router BRouter A

S0 10.1.2.2/24S0 10.1.2.2/24

DTE DCE

Figure RC-5-2 Networking diagram of configuring EIGRP timer





RouterA(config-if-Serial0)# ip address 192.1.1.1 255.255.255.0

RouterA(config-if-Serial0)# ip hello-interval eigrp 64 10

RouterA(config-if-Serial0)# ip hold-interval eigrp 64 30

! Configure EIGRP

RouterA(config)# router eigrp 64

RouterA(config-router-eigrp)# network 192.1.1.0

2) Configure Router B:


RouterB(config)#interface serial 0




5-17

RouterB(config-if-Serial0)# ip hello-interval eigrp 64 10

RouterB(config-if-Serial0)# ip hold-interval eigrp 64 30

! Configure EIGRP

RouterB(config)# router eigrp 64

RouterB(config-router-eigrp)# network 192.1.1.0

The following is the EIGRP neighbor table shown on Router B with show ip eigrpneighbors command. Please note that Router B has only one neighbor (192.1.1.1).

RouterB (config)# show ip eigrp neighbors


Address Interface Hold-time Update-time

192.1.1.1 serial 0 27 29:00

Now change the interval of sending Hello packets on Router A to 60 seconds.

Router A (config-if-Serial0)#IP hello-interval eigrp 64 60

Note that Router B will have no more neighbors. The reason is that Router A sendshello packet at an interval of 30s, but it still informs Router B that its hold time is 30s.After Router B receives the first hello packet, it advertises the cancellation of itsneighbor 192.1.1.1 (Router A) since it has not received hello packet from the neighborin another 30 seconds. Therefore, the hold time is specified in hello packet. If you wantto change the interval of sending hello packet, the hold time should also be changedand the hold time should be 3 times the interval of sending hello packet.

RouterB# show ip eigrp neighbors


Now change the interval of sending Hello packets on Router A to 180 seconds.

Router A(config-if-Serial0)# ip hold-interval eigrp 64 180

Again, you can see the neighbors in the table because the hold time is now 180sinstead of 30s.

RouterB# show ip eigrp neighbors


Address Interface Hold-time Update-time

192.1.1.1 serial 0 179 00:00:00

5.4.3 Configure EIGRP Passive Interface


In this example, passive interface allows EIGRP-configured router to cancel thetransmission on a specific, so that the router command is configured with moreinterfaces than in ideal case.

Three subnets are defined for Router A: 10.1.2.0/24, 10.1.2.0/24 and 10.1.3.0/24. Nowonly 10.1.2.1 needs to send EIGRP updating information, therefore interface S1(10.1.3.1) can be configured as passive.



5-18

When an interface is set to passive, no EIGRP packet will be sent through thatinterface,


Router

A

Router

B

Router

S0 10.1.3.2/24

S0 10.1.2.2/24

Passive interface

S0 10.1.2.1/24

4

S1 10.1.3.1/24

Figure RC-5-3 Networking diagram of configuring EIGRP passive interface



! Configure interface serial 0

RouterA (config)# interface serial 0

RouterA (config-if-Serial0)# ip address 10.1.2.1 255.255.255.0




RouterA (config)# router eigrp 64

RouterA (config-router-eigrp)# network 10.0.0.0

RouterA (config-router-eigrp)# no auto-summary

RouterA (config-router-eigrp)# passive interface serial 1





! Configure EIGRP

RouterB (config)# router eigrp 64

RouterB (config-router-eigrp)# network 10.0.0.0

RouterB (config-router-eigrp)# no auto-summary





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RouterC (config)#interface serial 0

RouterC (config-if-Serial0)# ip address 10.1.3.2 255.255.255.0

! Configure EIGRP

RouterC (config)# router eigrp 64

RouterC (config-router-eigrp)# network 10.0.0.0

RouterC (config-router-eigrp)# no auto-summary

5.4.4 Configuring EIGRP Route Summary


EIGRP can configure variable length route summary on the interface. All routes in thesummary area are summarized into one route and then sent out. In this way, you canreduce the routes to be sent and save bandwidth.

There are two routes 202.38.1.0/24 and 202.12.2.0/24 on Router A. They aresummarized into one route 202.0.0.0/8 with the command configured by Router B oninterface E0.


10.0.0.1/8e0

10.0.0.2/8e0 Router C

EthernetV.35/HDLC

202.38.1.1/24

129.102.1.1/16 129.102.1.2/16s0s0

dialer1

202.12.2.1/24dialer0

Router A Router B

Figure RC-5-4 Networking diagram of configuring EIGRP route summary


1) Configure Router A:RouterA (config)# router eigrp 10





RouterB (config)# router eigrp 10



Configure route summary on Ethernet 0

RouterB (config)# interface ethernet 0



5-20

RouterB (config-if-ethernet0)# ip summary-address eigrp 10 202.0.0.0 255.0.0.0

5.5 Troubleshooting of EIGRP

Fault 1: EIGRP does not work normally after startup.


l First use show running-config command to check whether the corresponding

interface is enabled with network command. If the interface is not enabled,

EIGRP will not transmit and receive messages through this interface, nor will itsend this interface route through other enabled interfaces.

l EIGRP is an IP-layer routing protocol, therefore IP layer must work normally.

Check whether physical connection or low layer protocol are normal, with pingcommand. If you cannot ping through the opposite router and the local router, it

means that the physical connection and lower layer protocol are faulty.l EIGRP sends hello packets in multicast mode. So when the lower layer

encapsulates X.25 (or similar link layer protocol such as frame relay), configure

map of the lower layer protocol into broadcast mode in order to transmit multicast

packets.

Example: while configuring X.25 mapping on serial 0, the IP address and X.121address of the opposite side are respectively 202.38.161.1 and 100, then theconfiguration shall be:

Quidway (config-if-serial0)#x25 map IP 202.38.161.1 100 broadcast

l EIGRP only receives EIGRP packets from the same AS. Check whether the AS

numbers of the neighboring routers are the same.

l If EIGRP configures MD5 authentication on the interface, it will perform MD5

authentication to the received packets. Those fails to pass the authentication willbe discarded. Check whether EIGRP MD5 authentication has been configured on

the interface or whether the authentication configuration is incorrect.

Fault 2: EIGRP can not redistribute other routing protocols.


l The metric of the redistributed routes must be specified when redistributing other

routing protocols, otherwise it will not work even if redistribute route command is

configured. You can use to two ways to set the metric of redistributed route: directsetting and default-metric setting.

Fault 3: EIGRP route authentication does not interwork.


l Check whether the configuration cryptographic keys are the same.

l Check whether the key-ids are the same.

l If it interworks with Cisco router, Cisco router uses cryptographic key of the

smallest key-id in key-chain. Please check whether the key-id and key-string



5-21

configuration of Quidway routers is the same as the configuration of minimum

key-chain of Cisco routers.


Chapter 6 Configuration of OSPF

6-1


6.1 Brief Introduction to OSPF

OSPF (Open Shortest Path First) is an autonomous, link-state-based internal routingprotocol developed by Internet Engineering Task Force (IETF). The current version isversion 2 (RFC1583), which features the following:

l Applicable range--- support network of various scales and hundreds of routers.l Fast convergence ----send updating message immediately after the topological

structure of the network is changed, so that the change can be synchronized in the

autonomous system.

l No self-loop ---- OSPF calculates the route with the shortest path tree algorithm

through the collected link status. This algorithm ensures that no self-loop route willbe generated.

l Area division ---- AS network can be divided into areas and the routing information

between the areas is further abstracted, reducing the bandwidth occupation in the

network.

l Equivalent route ----support multiple equivalent routes to the same destinationaddress.

l Route level --- the four levels of routes according to different priorities: intra-area

routes, inter-area routes, external route class 1 and external route class 2.

l Authentication ---- support interface-based message authentication to ensure the

security of the route computation.l Multicast ---packets are transmitted and received with multicast address on

multicasting link layer, greatly reducing interference to other network devices.

The entire network is composed of multiple ASs. The link state of AS is collected andtransmitted to find and spread route dynamically and then synchronize the informationof the AS. Each system is divided into areas. If a router port is allocated to multipleareas, it is an area boundary router (ABR) since it is located at the boundary andconnected with multiple areas. All ABSs and the routers between them form abackbone area, tagged with 0.0.0.0. All areas must be continuous logically. Thus,virtual link is introduced to the backbone to ensure that physically separated areas arestill connected logically. The route between the ASs is called autonomous systemboundary router (ASBR).

Computation of OSPF protocol is briefed as follows:

Each router that supports the OSPF protocol maintains a link state database (LSDB)that describes the topological structure of the whole autonomous system. Each routergenerates a link state broadcast (LSA) based on the surrounding network topologicalstructure. The LSA is sent to other routers together with the protocol message. In thisway, each router receives the LSA of all others. All LSAs put together will form theLSDB.



6-2

LSA describes the topological structure of one router while LSDB describes thetopological structure of the whole network. Router is easy to convert LSDB into adigraph with metric value. This graph exactly shows the topological structure of thewhole network. Obviously, all routers get the same graph.

1) Every router supporting OSPF maintains a Link State Database (LSDB for short)

describing the topology of the whole autonomous system. A router generates the

Link State Advertising (LSA for short) according to the network topology around itand sends the LSA to other routers on the network via the transmission of protocol

packets. Thus every router receives the LSA from other routers. All LSAs together

forms the LSDB.

2) The LSA describes the network topology around a router, so the LSDB describes

the topology of the whole network. A router can easily convert the LSDB into aweighted directed graph, which shows the real topology of the whole network.

Obviously, each router in the autonomous system will get the same topology

diagram of the network.

3) Each router calculates with SPF algorithm a shortest path tree with itself as the

root. This tree gives the routes to all autonomous systems. External routinginformation is the leaf sub-node. The external route is flagged by the router

broadcasting it to record additional information of the autonomous system.

Obviously, each router gets a different routing table.

In addition, multiple adjacent relations should be created so that each router on thebroadcast network and NBMA network can broadcast the local status information (suchas available interface information and reachable neighbor information etc) to the wholesystem. Consequently, the route change of any router may be transmitted many times,which is both unnecessary and wastes the precious bandwidth resources. To solve thisproblem, OSPF protocol selects “Designated Router” (DR). All routers sendinformation to DR, which will broadcast the network link status. Two non-DR routers(DR Other) will not create neighboring relation and not exchange any routinginformation. Then the number of neighboring relations between the routers on themulti-address network is greatly reduced.

OSPF protocol supports IP subnet and the marking and receiving of external routinginformation. It supports interface-based message authentication to ensure the securityof route calculation. Messages are transmitted and received in IP multicast mode.

OSPF software on VRP complies with the protocol text described in Internet RFC2328.Its main features are listed as follows:

l Support STUB area: Define the STUB area to save the overhead on receiving

ASE routing by local routers.l Share routing information with other dynamic routing protocols: at present stage,

RIP protocol and static routing can be received as external route of OSPF to the

autonomous system of a router. or the routing information found by OSPF be

distributed to other routing protocols.

l Authentication: OSPF supports plain text and MD5 encrypted passwordauthentication among adjacent routers within the same area.

l Flexible configuration of a router's interface parameters: OSPF parameters

supported include: output cost, Hello packet sending interval, retransmission



6-3

interval, interface transmission delay, routing preference, adjacent router dead

interval, authentication mode and authentication key.

l Virtual links--Virtual links can be created and configured.

l Abundant debugging information: OSPF provides abundant debugging

information to help the user in fault diagnosis.

6.2 Configuring OSPF

6.2.1 OSPF Configuration Task List

OSPF requires coordination among many routers (including routers inside and at theborder of an area, and routers at the boarder of an autonomous system).If noconfiguration is made, the default parameters will be used for the routers. And noauthentication will be made on the sending/receiving messages, the interface will notbelong to any area of an autonomous system. To change the default setting, theconfiguration of all the related routers should be consistent.

In all configuration tasks, OSPF, specified interface and area number should be startedfirst in order to configure other function features. But the configuration of interface-related function features is not restricted by whether OSPF has been enabled. It shouldbe noted that the original interface parameters become invalid after OSPF is closed.

OSPF configuration tasks are listed as follows:

l Specify Router ID

l Enable OSPF Routing Processl Associate an Area-id with the Specified Interface

l Configure the OSPF Network Type

l Specify the Cost of Sending a Packet on an Interface

l Specify the Router Priority

l Configure a Neighbor for NBMA Interfacel Specify the Hello Interval

l Specify the Dead Interval

l Specify the Re-transmitting Interval

l Specify the Transmit-delay

l Configure the Route Cost Sent to an OSPF STUB Areal Configure Route Summarization between OSPF Areas

l Create and Configure a Virtual Link

l Configure Authentication

l Configure Route Redistribution for OSPF

l Configure Parameters When Redistributing External Routesl Set Route Preference

6.2.2 Specify Router ID

Router ID is a 32-bit integral with symbol, the exclusive ID of a router in theautonomous system. If all interfaces of the router have not been configured with IP



6-4

addresses, the router ID must be configured in OSPF configuration mode, otherwiseOSPF will not run. It should be noted that the modified router ID takes effect after OSPFis restarted.

The user must configure the router ID, which should be same as the IP address of aspecific interface of this router.


Table RC-6-1 Specify router ID

Operation Command

Specify the router ID router id router-idDelete the router ID no router id

6.2.3 Enable OSPF Routing Process


Table RC-6-2 Enable OSPF routing process

Operation Command

Enable OSPF routing process and enter into the OSPF protocolconfiguration mode router ospf enable

Turn off an OSPF routing process no router ospf enable

By default, OSPF routing process is disabled.

6.2.4 Associate an Area-id with the Specified Interface

OSPF protocol divides the autonomous system into areas. Area is the logical group ofthe router. Some routers will belong to different areas (called area boundary routerABR), while a network segment can only be in one area. In other words, each interfacerunning OSPF protocol must be put in a specific area. The area is flagged with areaID.ABR transmits routing information between areas.

In addition, in the same area, all routers must agree unanimously to the parameterconfigurations of this area. So, in the configuration of routers in the same area, mostconfiguration data must be considered on basis of this area. Wrong configurations willmake it impossible for adjacent routers to transfer information to each other, or evenlead to the block or self-loop of routing information.


Table RC-6-3 Associate an area-id with the specified interface which runs OSPF routing process

Operation Command

Specify an area-id associated with the specified interface which runsOSPF routing process ip ospf enable area area-id

Delete an area-id associated with the specified interface no ip ospf enable area area-id

No area-id is associated with the specified interface by default after an OSPF routingprocess is enabled.



6-5

After OSPF routing process is enabled, you must specify an area-id associated with thespecified interface. OSPF only works on the specified interface.

6.2.5 Configure the OSPF Network Type

OSPF protocol calculates the route on the basis of the topological structure of theneighboring network of this router. Each router describes the topology of itsneighboring network and transmits to all other routers.

OSPF divides the network into 4 types according to the different link layer protocols:

l When the link layer is Ethernet, OSPF regards the network type as Broadcast by

default.l When the link layer protocol is frame relay, HDLC and X.25, OSPF regards the

network type as NBMA by default.

l No link layer protocol is considered as Point-to-Multipoint type by default. It is

usually manually modified from NBMA if the NBMA network is not wholly

interconnected.

l When the link layer protocol is PPP, LAPB, OSPF regards the network type asPoint-to-Point by default.

NBMA is a nonbroadcast multiaccess network. The typical network is X.25 and framerelay. Configure the poll-interval to specify the period of sending polling hello packetbefore this interface sets up neighboring relation with the adjacent routers.

The interface can be configured into nonbroadcast mode on the broadcast networkwithout multi-access capability.

If not all routers are inter-reachable on NBMA network, the interface can be configuredinto point-to-multipoint mode.

If the router has only one opposite terminal in NBMA network, the interface can also bechanged to point-to-point mode.

Difference between NBMA network and point-to-multipoint network:

l In OSPF protocol, NBMA refers to those fully connected, nonbroadcast andmulti-access networks. But point-to-multipoint network does not necessarily

require full connection.

l DR and BDR should be elected on NBMA while there is no DR or BDR on point-

to-point network.

l NBMA is a default network type. For example, if the link layer protocol is X.25 orframe relay, OSPF will regard the network type of this interface as NBMA (whether

the network is wholly connected). Point-to-multipoint is not a default network type.

No link layer protocol will be considered as point-to-multipoint because it must be

the modification from other network types. The most common practice is to

change the not fully connected NBMA to a point-to-multipoint network.l NBMA network sends messages in unicast mode and the neighbor should be

configured manually. In point-to-multipoint network, messages are sent either in

unicast mode or in multicast mode.




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Table RC-6-4 Configure the OSPF network type

Operation Command

Configure the OSPF network type ip ospf network-type { nonbroadcast | point-to-multipoint | point-to-point }

Delete the specified OSPF network type no ip ospf network-type { nonbroadcast | point-to-multipoint |point-to-point }

After an new OSPF network type is configured, the old network type on the interfacewill be replaced automatically.

6.2.6 Specify the Cost of Sending a Packet on an Interface

The user can configure the cost of sending a packet on the interface, otherwise OSPFwill automatically calculate the cost value according to the baud rate of the currentinterface.


Table RC-6-5 Specify the cost of sending a packet on an interface

Operation Command

Specify the cost of sending a packet on an interface ip ospf cost costReset the cost to the default value no ip ospf cost

The default value of the cost of sending a packet on the interface will be calculatedautomatically according to the interface baud rate as follows:

l If the interface baud rate < 2000bps or > 100000000bps

l The default cost would be: 100000000/64000 = 1562l Otherwise, the default cost would be: 100000000/ actual baud rate of the interface

6.2.7 Specify the Router Priority

The priority of router interface determines the qualifications of the interface in voting“Designated Router”. The interface with higher priority would be considered first whenthe voting rights conflict.

The designated router (DR) is not designated manually, but voted by all routers in thelocal network segment. The routers of Priority>0 in the local network segment can beused as the “Candidates”. The router with the greatest priority value will be selectedamong all routers that claim to be DR. If two routers have the same priority, choose theone with greater Router ID. The vote is Hello packet. Each router writes his DR into theHello packet and sends to all other routers on the network segment. When two routersin the same network segment claim to be “Designated Router” (DR), choose the onewith higher priority. If the priorities are equivalent, choose the one with greater router ID.If the priority of a router is 0, it will not be selected as “Designated Router” (DR) or“Backup Designated Router” (BDR).

If the DR fails due to a specific fault, a new DR should be voted, with synchronization.This may take a long time, during which route calculation is not correct. To shorten theprocess, OSPF puts forward the concept of BDR (Backup Designated Router). BDR isactually a backup of DR and is voted together with DR. BDR also creates neighboring



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relation with all routers in the network segment and exchanges routing information withthem. When DR fails, BDR will become the DR immediately without the need of re-election. With neighboring relation already created, this takeover process is instant. Ofcourse a new BDR needs to be elected again. Although it may take a long time, but theroute calculation will not be affected.

It should be noted that:

1) DR in the network segment is not necessarily the router with the highest priority.

By analogy, BDR is not necessarily the router with the second highest priority.

2) DR is a concept in a specific network segment, oriented to the router interface. A

router can be DR on one interface or BDR or DROther on another interface.

3) DR will be elected on broadcast interface or NBMA interface. It is not necessary onpoint-to-point interface or point-to-multipoint interface.


Table RC-6-6 Specify the router priority

Operation Command

Specify the router priority to determine the OSPF designated router to a network ip ospf priority valueReturn to the default router priority no ip ospf priority

By default, the interface priority in DR election is 0. It can be an integer ranging from 0to 255.

6.2.8 Configure a Neighbor for NBMA Interface

Some special configuration is needed for the network of NBMA interface. Since theadjacent router can not be found by broadcasting hello packets, the IP address of theadjacent router should be specified manually for the interface and whether the adjacentrouter has a voting right should also be specified. This is specified with commandneighbor Ip-address [priority value]. Before priority value is specified, this adjacentrouter is supposed to have no voting right.

On X.25 and frame relay network, map can be configured to make the whole networkfully connected (i.e. there is a virtual circuit between any two routers on the network andthey are directly reachable). Then OSPF can process like the broadcast network (suchas voting DR, BDR). Since the adjacent router can not be found dynamically bybroadcasting hello packets, the IP address of the neighboring router should bespecified manually for the interface and whether the adjacent router has a voting rightshould also be specified.


Table RC-6-7 Configure a neighbor for NBMA interface

Operation Command

Configure a neighbor for NBMA interface ip ospf neighbor ip-address [ eligible]Cancel or delete a neighbor for NBMA interface no ip ospf neighbor ip-address



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6.2.9 Specify Hello Interval

Hello packet is a most common message. It is sent to the adjacent routers periodically,used to find and maintain neighboring relation, select DR and BDR. The user can setthe interval of sending hello packets. The smaller the hello interval, the sooner thenetwork change will be found but the more network transmission is required. Thehello-interval values of routers in the same network segment must be the same. After arouter is started, it only sends hello packets to the neighboring points with the priorityover 0 (those routers that may be voted as DR or BDR). After DR and BDR are voted inthe network segment, they will send hello packets to all neighbors to create theneighboring relation.

On NBMA and point-to-multipoint networks, poll-interval should be configured tospecify the period of sending polling hello packet before this interface sets upneighboring relation with the adjacent routers.

poll-interval should be at least 3 times the hello-interval.


Table RC-6-8 Specify hello interval

Operation Command

Specify the length of time that software sends hello packet on the interface ip ospf hello-interval secondsReturn to the default hello interval time no ip ospf hello-intervalSpecify the length of poll-interval on NBMA and point-to-multipoint networktype ip ospf poll-interval seconds

Return to the default poll interval time no ip ospf poll-interval

By default, the hello-interval on point-to-point interface is 10 seconds and that onpoint-to-multipoint, nonbroadcast interfaces is 30 seconds. The default poll-intervalon the NBMA and point-to-multipoint interface is 120 seconds.

6.2.10 Specify Dead Interval

The dead-interval between adjacent routers refers to how long hello packets must nothave been seen before its neighbors declare the router down. The user can specifydead-interval, the period where the neighbor route fails. Dead-interval should be atleast 4 times of the Hello-interval. The dead-intervals of all routers in the same networksegment should be the same value.




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Table RC-6-9 Specify dead interval

Operation Command

Specify how long hello packets must not have been seenbefore its neighbors declare the router down ip ospf dead-interval seconds

Return to the default value of dead interval no ip ospf dead-interval

By default, the dead-interval on point-to-point interface is 40 seconds and that onpoint-to-multipoint, nonbroadcast interface is 120 seconds, ranging from 1 to 65535seconds.

Please note that when the user modifies the network type, hello-interval and dead-interval are both restored to their default values.

6.2.11 Specify Re-transmitting Interval

When a router sends LSA to its neighbors, it should wait for ACK messages from them.If ACK messages are not received from the neighbors after the retransmit interval, thisLSA should be retransmitted. The user can set the interval of re-transmitting LSA.


Table RC-6-10 Specify re-transmitting interval

Operation Command

Specify the time between link state advertisement re-transimissionto adjacencies to the interface

ip ospf retransmit seconds

Return to the default value of re-transmitting interval no ip ospf retransmit

By default, the re-transmitting interval is 5 seconds.

seconds should be twice greater than the period when a message is transmittedbetween two routers.

It should be noted that: The interval of re-transmitting LSA between adjacent routersshould not be so small as to cause unnecessary retransmission.

6.2.12 Specify Transmit-delay

In LSU message, transit-delay second should be added to LSA aging time beforetransmission. The time needed for transmitting messages on the interface should be inconsideration in the parameter setting.

LSA ages in “Link Status Database” (LSDB) of the local router (1 is added per second),but not in the process of network transmission. Therefore it is necessary to add theaging time before the transmission. This configuration is very important for low-speednetwork.




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Table RC-6-11 Specify transmit-delay

Operation Command

Specify the estimated number of seconds it takes to transmit alink state update packet on an OSPF interface ip ospf transmit-delay seconds

Return the default value of transmit-delay no ip ospf transmit-delay

By default, the time for transmit-delay is 1 second.

6.2.13 Configure the Route Cost Sent to an OSPF STUB Area

Stub area refers to the LSA area that does not transmit the received external route. Inthe area the routing table size and routing information transmission will be greatlyreduced. At this time, a default route will be broadcast to the area.

Stub area is an optional attribute but not all areas comply with the configurationcondition. Usually, stub area is located at the boundary of the autonomous system. It isthe non-backbone area with only one ABR or the area with multiple Bars but there is novirtual link configured between them.

To ensure that the route outside the autonomous system is still reachable, ABR of thisarea generates a default route (0.0.0.0) to be transmitted to into the area because allroutes outside the autonomous system are reachable through ABR.

In Stub area configuration, pay attention to the following points:

l Backbone area can not be configured into Stub area and virtual link can not go

through stub area.

l If an area is to be configured to a stub area, all routers in this area must beconfigured with this attribute.

l There should be no ASBR in Stub area, i.e. the route outside the autonomous

system can not be received into the area and the route outside the autonomous

system within the area can not be spread and transmitted out of the area.

Perform the following task in OSPF configuration mode.

Table RC-6-12 Configure the route cost sent to an OSPF STUB area

Operation Command

Configure the route cost sent to an OSPF STUB area stub cost cost area area-idDelete the route cost sent to an OSPF STUB area no stub cost cost area area-id

By default, stub area is not enabled. The cost of the default route sent to stub area is 1.

6.2.14 Configure Route Summarization between OSPF Areas

Route summary means that routing information is processed in ABR. Only one route issent to other areas for the network segment configured with summary. One area can beconfigured with multiple summary network segments so that OSPF can summarizemultiple network segments. When ABR sends routing information to other areas,Sum_net_Lsa (Type 3 LSA) is generated for each network segment. If there are some



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continuous network segments in the area, they can be summarized into one networksegment with range command. Then ABR only sends one summery LSA and all otherLSAs in the summary network segment range specified with this command will not besent separately, which downsize the LSDB in other areas. The configuration of range isonly effective when it is configured on ABR in stub area.

For example: there are two network segments in an area as follows:

202.38.160.0 255.255.255.0

202.38.180.0 255.255.255.0

There are summarized into one network segment:202.38.0.0 255.255.0.0

When the summary network segment of a specific network is added to an area, theinternal routes with the IP addresses that fall in this summary network segment in thisarea will not be broadcast separately to other areas. Only the abstract information ofthe route of the whole summary network segment is broadcast. If the network segmentrange is restricted with key words notadvertise , the abstract information to thisnetwork segment route will not be broadcast. This network segment is described in theform of IP address/mask. Receiving the summary network segment and the restrictionof the network segment can reduce the inter-area routing information.

Please note that route summary is only effective when configured on ABR.


Table RC-6-13 Configure route summarization between OSPF areas

Operation Command

Configure route summarization between OSPF areas range address mask area area-id [ advertise | non-advertise ]

Cancel route summary between areas no range address mask area area-id

By default, inter-area routes are not summarized.

6.2.15 Create and Configure a Virtual Link

After OSPF area division, all areas are not equal. One area is unique. It is called thebackbone area with the area-id of 0.0.0.0. OSPF route updating between non-backbone areas is carried out through the backbone area. OSPF protocol requires thatall non-backbone areas must be connected with the backbone area, i.e. at least oneport on ABR should be in the area 0.0.0.0.If there is no physical connection between anarea and the backbone area 0.0.0.0, a virtual link must be created.

If physical connection is not possible due to the limitation of network topologicalstructure, a virtual link can satisfy this requirement. Virtual link refers to a logicalconnection channel between two ABRs created through an area of non-backbone areainternal routes. Both ends of the virtual link must be ABRs and both ends must beconfigured at the same so that the virtual link can take effect. Virtual link is flagged withthe ID of the opposite router. The area providing the non-backbone internal route forboth ends of the virtual connection is called a transit area, whose area-id should also bespecified in configuration.

The virtual link is activated after the route through the transit area is calculated. It isequivalent to a point-to-point connection between two terminals. Parameters can beconfigured for this connection like a physical interface, such as sending hello-interval.



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“Logic Channel” means that multiple routers running OSPF between two ABRs onlyforward messages (since the destination addresses of the protocol messages are notthese routers, the messages are transparent to them and they are transmitted asordinary IP messages), while routing information are transmitted directly between twoABRs. Routing information here means LSA of type3 generated by ABR. Thesynchronization of routers in the area is not changed.

Please note that if the autonomous system is divided into more than one area, onemust be the backbone area, other areas must be connected with the backbone areadirectly or logically and the backbone area itself should be well connected too.


Table RC-6-14 Create and configure a virtual link

Operation Command

Create and configure a virtual linkvirtual-link neighbor-id router-id transit-area area-id [ hello-intervalseconds ] [ retransmit seconds ] [ transit-delay seconds ] [ dead-intervalseconds ]

Delete the specified virtual link no virtual-link neighbor-id router-id transit-area area-id

By default, there is no virtual link is created. area-id and router-id has no default value.hello-interval is 10 seconds, retransmit-interval is 5 seconds, transmit-delay is 1second and dead-interval is 40 seconds.

6.2.16 Configure Authentication

OSPF supports plain text authentication and MD5 authentication between adjacentrouters.


Table RC-6-15 Configure authentication

Operation Command

Specify a password for OSPF plain text authentication ip ospf authentication simple passwordSpecify the string and key-id for OSPF MD5 authentication ip ospf authentication md5 string key-idCancel authentication on the interface no ip ospf authentication

By default, the interface will not authenticate OSPF packet.

The maximum length of password for plain text authentication is 8 characters and thestring for MD5 authentication is 16 characters maximum. key-id is the key value of MD5authentication, ranging from 1 to 255.

6.2.17 Configure Route Redistribution for OSPF

The dynamic routing protocols on the routers can share the routing information. Due toOSPF features, the routes found by other routing protocols are always regarded as theroutes outside the autonomous system in processing. In the receiving command, thecost type of the route, cost value and flag can be specified to overlap default routingparameters (see “Configure Default Options of OSPF Receiving External Route”configuration).



6-13

OSPF uses 4 different route types, whose sequence runs:

l Intra-area route

l Inter-area route

l External router Type 1l External router Type 2

Intra-area route is the route in an area of the autonomous system and inter-area routeis the route between different areas of the autonomous system. They are all routes inthe autonomous system.

The external route describes how to select the route to a destination outside theautonomous system.

External route Type 1 refers to the received IGP route (such as RIP, IGRP, STATIC).The reliability of this route is high, so the calculated cost of the external route and thecost of the route inside the AS are in the same numeric level and it is comparable withthe cost of OSPF route, i.e. the cost value of external route Type 1 = the cost value fromthe local router to the corresponding ASBR + the cost value from ASBR to thedestination address of the route.

External route Type 2 refers to the received EGP route. The reliability of this route is low,therefore OSPF protocol takes the cost from ASBR to the outside autonomous systemas much more than that to ASBR within the automatic system. Therefore mainly theformer is considered in the calculation of route cost, i.e. the cost value to the externalroute Type 2 = the cost value from ASBR the route destination address. If the valuesare equal, consider the cost value from the local router to the corresponding ASBR.


Table RC-6-16 Configure route redistribution for OSPF

Operation Command

Configure route redistribution for OSPF redistribute ospfase protocol [ process-id ] [ metric metric ] [ type1 | 2 ] [ tag tag-value ]

Cancel route distribution for OSPF no redistribute ospfase protocol

By default, OSPF does not redistribute routes from other domain into the routing table.

protocol specifies the source routing domain that can be redistributed. At present, igrpcan redistribute routes domain such as connected, static, rip, igrp, eigrp and bgp.


6.2.18 Configure Parameters when Redistributing External Routes

When the routes found by other routing protocols on the router are received by OSPFas the external routing information of its own autonomous system, some otherparameters are needed, including the default cost and default tag of the route. Routertag can be used to identify the information related to the protocol, such as the numberOSPF uses as the autonomous system number when receiving BGP protocol.

OSPF specifies two types of cost selection modes of external routing information in theprotocol. The user can configure receiving the default cost type of the route.



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Table RC-6-17 Configure parameters when redistributing external routes

Operation Command

Configure the default cost value when OSPF redistributing externalroutes default redistribute cost cost

Return to the default cost value when OSPF redistributing externalroutes no default redistribute cost

Configure the interval for OSPF redistributing external routes default redistribute interval secondsReturn to the default interval value for OSPF redistributing externalroutes

no default redistribute intervalseconds

Configure the upper limit of routes that OSPF can redistribute default redistribute limit routesRestore default value of routes that OSPF can redistribute no default redistribute limitConfigure the default tag value when OSPF redistributing externalroutes default redistribute tag tag

Return to the default tag value when OSPF redistributing externalroutes no default redistribute tag

Configure the default type when OSPF redistributing external routes default redistribute type { 1 | 2 }Return to the default route type when OSPF redistributing externalroutes no default redistribute type

By default, there is no cost value and tag value when external route is redistributed.The redistributed route is external route Type 2, the interval of redistributing externalroute is 1 second and at most 150 external routes can be redistributed in each interval.


Multiple dynamic routing protocols may run on the router at the same time, the problemof information sharing and selection between the routing protocols occurs. The systemsets a priority for every routing protocol. When several protocols find the same route,the protocol with higher priority will function.

Perform the following task in protocol configuration mode.


Operation Command

Specify OSPF route preference preference [ ase ] valueReturn the default value of OSPF route preference no preference [ ase ]

By default, OSPF route preference is 10. The preference of the redistributed externalrouting protocol is 150.

6.2.20 Configure Route Filter for OSPF


1) Configure filtering route information received by OSPF

Table RC-6-19 Filter route information received by OSPF

Operation Command

Filter the routing information received distribute-list access-list-number inChange or cancel filtering routing information received no distribute-list access-list-number in



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By default, OSPF does not filter any route information received.


6.3 Monitoring and Maintenance of OSPF

Table RC-6-20 Monitoring and maintenance of OSPF

Operation Command

Show OSPF main information show ip ospfShow OSPF external routing information show ip ospf aseShow OSPF statistic information show ip ospf cumulativeShow OSPF LSDB information show ip ospf database [ retranse ]Show OSPF error information show ip ospf errorShow OSPF interface information show ip ospf interface-type interface-number

Show OSPF LSDB detailed informationshow ip ospf lsa [ router_lsa | net_lsa | sumnet_lsa |asbr_lsa | external_lsa | adv_rtr | self_originate | ls_id ][ area area-id ]

Show OSPF neighboring point information show ip ospf neighborShow OSPF nexthop information show ip ospf nexthopShow OSPF routing table information show ip ospf routingShow OSPF virtual link information show ip ospf virtual-linksTurn on the OSPF debugging packet switches debug ip ospf { event | packet | lsa | spf }

1) Show OSPF main information

Quidway(config)# show ip ospf

RouterID: 0.0.0.1 Border Router: Area

Routing preference: Inter/Intra: 10 External: 150

Default ASE parameters: Metric: 1 Tag: 0.0.0.1 Type: 2

SPF computation count: 73

Area 0.0.0.0:

Authtype: none Flags: <>

SPF scheduled: <>

Interface: 10.10.0.2 (Serial0) --> 10.10.0.1

Cost: 10 State: P To P Type: PointToPoint

Priority: 1

DoNotAge Lsa Allowed

Timers: Hello 10, Dead 40, Poll 0, Retransmit 5

Area 0.0.0.1:

Authtype: none Flags: <>

SPF scheduled: <>

Interface: 10.110.10.1 (Ethernet0)

Cost: 10 State: DR Type: Broadcast

Priority: 1

Designated Router: 10.110.10.1



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DoNotAge Lsa Allowed

Timers: Hello 10, Dead 40, Poll 0, Retransmit 5

2) Show OSPF LSDB information

Quidway(config)# show ip ospf database

Link State Database

Area: 0.0.0.0

TypeLinkStateID AdvRouter Age Len Sequence Metric Where

Stub 10.10.0.0 0.0.0.1 388 24 0 0 SpfTree

Rtr 0.0.0.1 0.0.0.1 362 48 8000002f 0 SpfTree

Rtr 0.0.0.2 0.0.0.2 389 48 8000002e 0 SpfTree

SNet 10.110.0.0 0.0.0.1 193 28 80000003 10 Inter List

Area: 0.0.0.1


Stub 10.110.0.0 0.0.0.1 2074 24 0 0 SpfTree

Rtr 0.0.0.1 0.0.0.1 363 36 80000003 0 SpfTree

SNet 10.10.0.0 0.0.0.1 193 28 80000002 10 Inter List

ASB 0.0.0.2 0.0.0.1 193 28 80000002 10 SumAsb List

AS External Database


ASE 2.2.0.0 0.0.0.2 278 36 80000001 1 initialized

3) Show OSPF neighboring point information

Quidway(config)# show ip ospf neighbor

Area 0 interface 10.10.0.2 (Serial0)'s neighbors

RouterID: 0.0.0.2 Address: 10.10.0.1

State: Full Mode: Slave Priority: 1

DR: None BDR: None

Last Hello: 1:11:25 Last Exchange: 55:35

show ip ospf neighbors command displays OSPF information of neighbor router. Ifrouter ID is not specified, the command will show the information of all OSPF neighbors.The most important information shown with the command is the neighboring status.This command is also used to locate OSPF network fault.

6.4 Typical Configuration of OSPF

6.4.1 Configure OSPF on the Point-to-Multipoint Interface


l Router A communicates with Router B through DLCI 101 and communicates with

Router B through DLCI 102.



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l Router B communicates with Router A through DLCI 201, communicates with

Router C through DLCI 202 and communicates with Router D through DLCI 203.

l Router C communicates with Router B through DLCI 301.

l Router D communicates with Router A through DLCI 401 and communicates with

Router B through DLCI 402.


FR

10.0.0.1 10.0.0.2

10.0.0.3 10.0.0.4

101201

203202102

401

402

301

Router A Router B

Router D Router C

Figure RC-6-1 Networking diagram of configuration of running OSPF on point-to-multipoint interface



! Configure the ip address of interface Serial0, encapsulated into frame relay andconfigure frame relay mapping table.

RouterA(config)# interface serial 0



RouterA(config-if-Serial0)# frame-relay map IP 10.0.0.2 101





RouterA(config-if-Serial1)# frame-relay map ip 11.0.0.2 102

! Enable OSPF

RouterA(config)# router id 1.1.1.1

RouterA(config)# router ospf enable

! Configure the area-id of the interface and the interface type

RouterA(config-if-Serial0)# ip ospf enable area 0



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RouterA(config-if-Serial0)# ip ospf network-type point-to-multipoint

RouterA(config-if-Serial0)# ip ospf neighbor 10.0.0.2


RouterA(config-if-Serial0)# ip ospf neighbor 10.0.0.4





RouterB(config-if-Serial0)# encapsulation frame-relay

RouterB(config-if-Serial0)# frame-relay map ip 10.0.0.1 201





RouterA(config-if-Serial1)# frame-relay map ip 12.0.0.2 202

! Enable OSPF

RouterB(config)# router id 2.2.2.2

RouterB(config)# router ospf enable


RouterB(config-if-Serial0)# ip ospf enable area 0

RouterB(config-if-Serial0)# ip ospf network-type point-to-multipoint

RouterB(config-if-Serial0)# ip ospf neighbor 10.0.0.1

RouterB(config-if-Serial1)# ip ospf neighbor 12.0.0.2





RouterC(config-if-Serial1)# encapsulation frame-relay

RouterC(config-if-Serial1)# frame-relay map IP 12.0.0.1 301

! Enable OSPF routing process

RouterC(config)# router id 3.3.3.3

RouterC(config)# router ospf enable



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RouterC(config-if-Serial0)# ip ospf enable area 0

RouterC(config-if-Serial0)# ip ospf network-type point-to-multipoint

RouterC(config-if-Serial0)# ip ospf neighbor 10.0.0.1

4) Configure Router D:


RouterD(config)# interface serial 1

RouterD(config-if-Serial1)# ip address 11.0.0.2 255.0.0.0

RouterD(config-if-Serial1)# encapsulation frame-relay

RouterD(config-if-Serial1)# frame-relay map IP 11.0.0.1 401

! Enable OSPF routing process

RouterD(config)# router id 4.4.4.4

RouterD(config)# router ospf enable


RouterD(config-if-Serial1)# ip ospf enable area 0

RouterD(config-if-Serial1)# ip ospf network-type point-to-multipoint

RouterD(config-if-Serial1)# ip ospf neighbor 11.0.0.1

6.4.2 Configure DR on OSPF Preference


The following example describes the preference configuration of several routers in anOSPF autonomous system. The preference of Router A is 100, the highest on thenetwork, therefore Router A is selected as DR. Router C is of the second highestpriority, therefore is chosen as BDR. The preference of Router B is 0, which means thatit can not be a DR. Router D has no preference, so the default value 1 is taken.


BDRRouter B

Router a Router D

Router C

E0 192.1.1.1/24 E0 192.1.1.4/24

E0 10.1.2.3/24E0 192.1.1.2/24

DR1.1.1.1 4.4.4.4

3.3.3.32.2.2.2



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Figure RC-6-2 Networking diagram of configuring “DR” selection of OSPF preference





RouterA(config-if-Ethernet0)# ip ospf priority 100



RouterA(config-if-Ethernet0)# ip ospf enable area 0


RouterB(config)#interface ethernet 0


RouterB(config-if-Ethernet0)# ip ospf priority 0


RouterB(config)#router ospf enable

RouterB(config-if-Ethernet0)# ip ospf enable area 0




RouterC(config-if-Ethernet0)# ip ospf priority 2



RouterC(config-if-Ethernet0)# ip ospf enable area 0


RouterD(config)#interface ethernet 0

RouterD(config-if-Ethernet0)# ip address 192.1.1.4 255.255.255.0

RouterD(config-if-Ethernet0)# router id 4.4.4.4


RouterD(config-if-Ethernet0)# ip ospf enable area 0

Run show ip ospf neighbor on Router A to show OSPF neighbor. Note that Router Ahas 3 neighbors.

RouterA(config)# show ip ospf neighbor

Neighbor pri State Address Interface

4.4.4.4 1 full/DRother 192.1.1.4 Ethernet0



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3.3.3.3 2 full/BDR 192.1.1.3 Ethernet0


The status of every neighbor is full, which means that Router A has createdneighboring relation with all neighbors. Only DR and BDR have created neighboringrelation with all routers on the network. Router A is DR and Router C is BDR on thenetwork. All other neighbors are DRother, which means that they are neither DR norBDR.

Change the preference of Router B to 200:

Router B(config-if-Ethernet0)# ip ospf priority 200

Run show ip ospf neighbor on Router A to show OSPF neighbors. Note that thepreference of Router B has been changed to 200, but it is not DR.

RouterA(config)# show IP ospf neighbor





Only when the DR no longer exists on the network will DR be changed. Shut downRouter A and run show ip ospf neighbor on Router D to display neighbors. Note thatRouter C, which was BDR, now becomes DR and so does Router B.

RouterD(config)# show ip ospf neighbor



2.2.2.2 200 full/DR 192.1.1.2 Ethernet0

Shut down the router and restart again will lead to the reelect of DR and BDR. Restartrouter A and run show ip ospf neighbor command to display neighbors. Note thatrouter B is elected DR (whose preference is 200) and Router A becomes BDR (whosepreference is 100).

RouterD# show ip ospf neighbor

Neighbor pri State Deadtime Address Interface

1.1.1.1 100 full/BDR 00:00:33 192.1.1.1 E0

3.3.3.3 2 2way/DRother 00:00:33 192.1.1.3 E0

2.2.2.2 200 full/DR 00:00:30 192.1.1.2 E0

6.4.3 Configure OSPF Autonomous System


The following example describes the configuration of several routers in an OSPFautonomous system. In this example, the 5 routers in AS1 are configured with OSPFprotocols.

l Router A and Router B are both internal routers in area 1.l Router C is the ABR of OSPF. The E3 port of this router is connected with area 1

and S0 is connected with area 0.



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l Router D is the internal router of area 0 (backbone area).

l Router E is the boundary router of OSPF autonomous system. RIP routes will be

imported to OSPF and these routes will be broadcast by OSPF.


Area1

Ethernet

Ethernet

AS1

Area0

S0

S1

E2 131.109.1.2

131.109.2.4

E3 131.109.1.3

E1 131.109.1.1

131.109.2.3

E5 10.0.0.5

11.0.0.6 in AS211.0.0.5

E4 10.0.0.4

S2

Router BRouter A

Router C

Router D

Router E

Figure RC-6-3 Networking diagram of configuring OSPF autonomous system

III. Configuring procedure

1) Configure Router A (intra-area router):






2) Configure Router B (intra-area router):






3) Configure Router C (area boundary router):





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4) Configure Router D (intra-area router):

RouterD(config)# interface ethernet 0

RouterD(config-if-Ethernet0)# ip address 10.0.0.4 255.0.0.0

RouterD(config)# router id 4.4.4.4


RouterD(config-if-Ethernet0)# ip ospf enable area 0



RouterD(config-if-Serial0)# ip ospf enable area 0

5) Configure Router E (ASBR):

RouterE(config)# interface ethernet 0

RouterE(config-if-Ethernet0)# ip address 10.0.0.5 255.0.0.0

RouterE(config)# router id 5.5.5.5

RouterE(config)# router ospf enable

RouterE(config-if-Ethernet0)# ip ospf enable area 0

RouterE(config)# interface serial 1

RouterE(config-if-Serial1)# ip address 11.0.0.5 255.0.0.0

RouterE(config-if-Serial1)# ip ospf enable area 0

RouterE(config-if-Serial1)# router ospf enable

RouterE(config-router-ospf)# redistribute ospf-ase rip type 1

6.4.4 Configure OSPF Virtual Link


Area 4 is not directly connected with area 0 in the following diagram. Area 1 serves asthe transit area to connect area 4 and area 0. Configure a virtual link between Router Band Router C.



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Router

Router

Router

E0 192.1.1.1/24

E0 152.1.1.1/24

E0 192.1.1.2/24

Router A1.1.1.1

Router B2.2.2.2

VirtualLink

E0 193.1.1.2/24

Area 4

Area 1

Area 0

Router C3.3.3.3

Figure RC-6-4 Networking diagram of configuring OSPF virtual link












RouterB(config-if-Serial)# ip address 193.1.1.2 255.255.255.0




RouterB(config-if-Serial0)# ip ospf enable area 1

RouterB(config-router-ospf)# virtual-link neighbor-id 3.3.3.3 transit-area 1






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RouterC(config-if-Serial)# ip address 193.1.1.1 255.255.255.0





RouterC(config-router-ospf)# virtual-link neighbor-id 2.2.2.2 transit-area 1

6.4.5 Configure OSPF Neighbor Authentication


Verify neighbor authentication with plain text algorithm and MD5 algorithm. Plain textauthentication is used when Router A and Router B exchange route updating and MD5authentication is used when Router A and Router C exchange route updating. TheEthernet interface of Router A and that of Router B are in OSPF area 0.The serial portof Router A and that of Router B are both in area 1, configured with MD5 authentication.


Area 0

Area 1

E0 192.1.1.2

S0 193.1.1.2

S0 193.1.1.2

MD5 authentication

Simple authentication

0000

2.2.2.2

Area 0

1.1.1.1

3.3.3.3

Router A

Router B

Router C

Figure RC-6-5 Networking diagram of configuring OSPF neighbor authentication





RouterA(config-if-Ethernet0)# ip ospf authentication simple quidway



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RouterA(config-if-Serial0)# ip ospf authentication md5 huawei 11








RouterB(config-if-Ethernet0)# ip ospf authentication simple quidway







RouterC(config-if-Serial0)# ip ospf authentication md5 huawei 11




6.5 Troubleshooting of OSPF Configuration

Fault 1: If you have configured OSPF as described above, but router OSPF fails to runnormally.


1) Troubleshooting local area: First check whether the protocol between the two

directly connected routers is running normally. If the neighbor state machine

between the two routers is in FULL status, it means the protocol is runningnormally. (Note: on broadcast network and NBMA network, the neighbor state

machine between two DROther routers is not in FULL status but in 2 way status.

DR, BDR and all other routers are in FULL status).

Use show ip ospf neighbor command to view:

Quidway# show ip ospf neighbor

Interface: 202.38.160.1 Area: 0.0.0.2 Neighbors:



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RouterID: 2.2.2.2 Address: 202.38.160.2

State:FULL Mode: None Priority: 0

DR: 202.38.160.1 BDR: 202.38.160.1

Last Hello: 14:04 Last Exchange: 0

Authentication Sequence: a51dac

View OSPF information on the interface with show ip ospf interface command.

l Check whether the physical connection and low layer protocol are running

normally. If the opposite router cannot ping through the local router, it means that

the physical connection and lower layer protocol are faulty.

l If the physical connection and lower layer protocol are normal, check the OSPF

parameters configured on the interface. The parameters must be the same asthose of the adjacent routers of this interface. The parameters include hellointerval,

deadinterval and authentication. Area-id must be the same and the network

segment and mask must be consistent (the network segment and mask of point-

to-point and virtual link can be different).

l Check whether deadinterval value is at least 4 times the hellointerval value on thesame interface.

l If the network type is NBMA or point-to-multipoint, or the interface type is manually

modified to point-to-point, use command Quidway (config-if-SerialX)# ip ospf

network-type point-to-point to manually specify Neighbor. In addition: when two

routers are connected in dial-up mode, although PPP protocol is encapsulated onthe link layer, it is still NBMA type. Neighbor should be specified manually. Use

command Quidway(config-if-SerialX)# ip ospf neighbor ip-address.

l If the network type is broadcast network or NBMA, at least the priority of one

interface should be over 0.

l If an area is configured to a stub area, all routers connected with this area must beconfigured to stub areas.

l The interface type of two adjacent routers must be the same.

l If two or more areas are configured, at least one area should be configured into

backbone area (area 0).

l Make sure the backbone area is connected with all areas.l Virtual connection can not go through stub area.

2) Global troubleshooting: If the above steps are correct, but OSPF still can not find

the remote route, check the following configuration.

l If two or more areas are configured for one router, at least one area should be

configured into backbone area (the area-id of one area should be 0 or a virtual linkshould be configured).

As shown in the following diagram, only one area is configured on Router A and RouterD and two areas are configured respectively for Router B(area0, area1) and RouterC(area1, area2). One area in Router B is 0, which satisfies the requirement. However,none of the two areas in Router C is 0. In such case a virtual link must be configuredbetween Router C and Router B.



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Make sure area 2 and areas 0 (backbone area) are connected.

RTA RTB RTC RTDarea0 area1 area2

Figure RC-6-6 OSPF area schematic diagram

l The virtual link can not go through stub area and the backbone area (area 0) can

not be configured as stub area. That is to say, if a virtual link is configured between

Router B and Router C, area 1 can not be configured as stub area, nor can area 0.

In the above diagram, only area 2 can be configured as stub area.

l The router in the stub area can not receive external route, i.e. Router D can notreceive external route.

l Make sure the backbone areas are connected.


Chapter 7Configuration of BGP

7-1

Chapter 7 Configuration of BGP

7.1 Brief Introduction of BGP

Border Gateway Protocol (BGP) is a dynamic route discovering protocol betweenautonomous systems, which automatically switches loopless routing informationbetween autonomous systems. By switching path reachable information withautonomous area number (AS) sequence attributes, it constructs the topologicaldiagrams of the autonomous areas so as to eliminate route loops and carry out userconfigured strategies. BGP protocol is usually used between ISPs.

BGP protocol has been used since 1989. The three earliest versions are RFC1105(BGP-1), RFC1163 (BGP-2) and RFC1267 (BGP-3). The currently used is RFC1771(BGP- 4). It applies to the distributed structure and supports classless interdomainrouting (CIDR). BGP-4 has become the actual standard of Internet external routingprotocol. It features the following:

l BGP is an external routing protocol, oriented to control route spreading and select

best route rather than find and calculate route. This is different from the internal

routing protocol.l Completely resolve route loop problem by carrying AS path information.

l Use TCP as the transmission layer protocol, improving the reliability of the

protocol.

l BGP-4 supports classless interdomain routing (CIDR), or supernetting. This is a

great enhancement from BGP-3.CIDR judges the IP address in a totally new way.It no long recognize network class A, network class B or network class C. For

example, with CIDR, an illegal class C network address 192.213.0.0 (255.255.0.0)

is indicated as 192.213.0.0/16, which is a legal supernetwork. /16 means that the

subnet mask is 16bit starting from the left of the address. The introduction of CIDR

simplifies the route aggregation. Route aggregation is the combination of severalroutes. Thus one route instead of several routes will be distributed and the routing

table is simplified.

l When route is updated, BGP only sends increment route. In this way BGP

occupies much less bandwidth in transmitting route. It applies to the transmission

of large amount of routing information on Internet.l For political and economic reason, each autonomous system wants to filter, select

and control the routes. BGP-4 provides abundant routing strategies for easy

expansion of BGP to support new development of Internet.

BGP system runs on a specific router as a high layer protocol. On the system startup,the whole BGP routing table is transmitted for the exchange of routing information.Later on, only update message is transmitted for updating routing table. In the systemrunning, keep-alive messages are received and transmitted to check whether theconnection between routers is normal.



7-2

The router transmitting BGP message is called BGP speaker. It receives and generatesnew routing information from time to time and advertises to other BGP speakers. WhenBGP speaker receives a new route advertisement from other autonomous systems, ifthis route is better than the existing route or there is no acceptable route currently, BGPspeaker will broadcast this route to all other BGP speakers in the autonomous system.BGP speakers are peers to each other. Several related peers form a peer group.

BGP runs on the router in two modes:

l IBGP (Internal BGP)l EBGP (External BGP)

When routers in an autonomous system exchange network reachable information,IBGP is run. When routers of different autonomous systems exchange networkreachable information, EBGP is run.

BGP protocol machine is driven by messages which can be devided into 4 categories.

l Open message

l Update message

l Notification messagel Keep-alive message

open message is the first transmitted message after the connection is created. It isused to create connection between BGP peers. notification message notifies errors.keep-alive message is used to check the validity of the connection. update message isthe most important message in BGP system, and used to switch routing informationamong the peers. It consists of three parts: unreachable route, path attributes andNetwork Layer Reachability Information (NLRI).

7.2 Configuring BGP

7.2.1 BGP Configuration Task List

BGP configuration tasks are listed as follows:

l Enable BGP Routing Processl Associate a network with a BGP routing process

l Configure the BGP MED Metric

l Comparing MED values from different AS neighbor path

l Specify Route Preference

l Adjust BGP Timersl Configure BGP Neighbors

l Configure BGP Peer Groups

l Configure BGP aggregation

l Configure a Route Reflector

l Configure Community Attributel Configure a Route Domain Confederation

l Configure Route Dampening

l Configure Synchronization of BGP and an IGP

l Configure Interaction between BGP and IGP



7-3

l Set Route Preference

l Configure Route Redistribution for BGP

l Create a Access-list, AS path list and route-map

l Reset BGP connections

7.2.2 Enable BGP Routing Process

Specify the local autonomous system number (AS number) when a BGP routingprocess is enabled. After a BGP routing process is enabled, the local router will notaccept BGP connection request from the neighbor routers. To make the local routersend BGP connection request to the neighbor routers, refer to the neighbor command.When BGP routing process is turned off, BGP protocol will close all BGP connectionsthat have been created.


Table RC-7-1 Enable BGP routing process

Operation Command

Enable BGP routing process and enter into the BGP protocolconfiguration mode router bgp as-number

Turn off the BGP routing process no router bgp

By default, BGP routing process is disabled.

7.2.3 Associate a network with a BGP routing process

Perform the following task in BGP protocol configuration mode.

Table RC-7-2 Associate a network with a BGP routing process

Operation Command

Specify a lists of networks associated with aBGP routing process

network ip-address [ mask address-mask ] [ route-mapmap-name ]

Delete a lists of networks associated with a BGProuting process

no network ip-address [ mask address-mask ] [ route-mapmap-name ]

By default, a lists of networks is not associated with BGP routing process.

7.2.4 Configure the BGP MED Metric

Attribute of Multi-Exit Discriminators (MED) is the external metric of a route. It isdifferent from the local preference attribute. MED is switched between ASs and theMED that has entered AS will not leave the AS. AS uses local attribute for its ownout-site selection processing while MED attribute is used to select the best route. Theroute with small MED value should be selected. When a router running BGP getsroutes with the same destination address but different next hop through differentexternal peers, it will make a preference selection based on the MED values. The routewith smaller MED value will be used as the external route of the system while otherconditions are the same.



7-4

To operate the MED attribute, an access control list is used to indicate what network willbe operated.


Table RC-7-3 Configure the BGP MED metric

Operation Command

Set a Multi-Exit Discriminator default-metric metricRestore a Multi-Exit Discriminator to its default value no default-metric

By default, the default value of a Multi-Exit Discriminator is 0.

7.2.5 Allow the Comparison of the MED for Paths

It is used to select the best route. The route with smaller MED value will be selected.


Table RC-7-4 Allow the comparison of the MED for paths

Operation Command

Allow the comparison of the MED for paths from neighbors in different AS bgp always-compare-medDisallow the comparison of the MED for paths from neighbors in different AS no bgp always-compare-med

By default, the comparison of the MED for paths from neighbors in different AS isdisabled.

This configuration should not be used unless it is sure that different AS use the sameIGP and routing modes.

7.2.6 Change the Local Preference Value

Configuring different local preferences will affect BGP routing selection. When a routerrunning BGP gets routes with the same destination address but different next hopsthrough different internal peers, it will select the route of highest local preference to thisdestination.


Table RC-7-5 Change the local preference value

Operation Command

Change the local preference value bgp default local-preference valueRestore the local preference value to its default value no bgp default local-preference

By default, the value of local preference is 100.



7-5

7.2.7 Adjust BGP Timers

The interval of sending Keepalive messages required by RFC and BGP holdtime areimportant parameters in BGP protocol.

When a router has created BGP connection successfully with the opposite router, itsends Keepalive messages to the opposite router with the time interval set bykeepalive-interval to indicate whether the connection channel is normal. Generally, thetime interval of sending Keepalive message is one third of that of Holdtime.

Holdtime-interval is the time interval of continuously receiving Keepalive and Updatemessage. If Keepalive or Update message is received, the holding timer will be reset. Ifa router If a router has not received any messages from the opposite router for aspecific period of holding time, this BGP connection will be considered broken and becut off. The router can negotiate with its opposite router and set the holding time to theshorter one.




7-6

Table RC-7-6 Adjust the BGP timers

Operation Command

Adjust BGP network timers for all neighbors timers bgp keepalive-interval holdtime-intervalRestore BGP network timers to their default value no timers bgp

By default, the interval of sending keepalive packet is 60 seconds, ranged from 1 to4294967295 seconds. Timer holdtime is 180 seconds, ranging from 3 to 42949675seconds.

7.2.8 Configure Neighbors

Perform the following peer configuration in BGP protocol configuration mode.

I. Configure a BGP Neighbor to be a Member of a Peer Group

Add one BGP peer into the peer group and get the configuration of the peer group.When the configuration of the peer group is changed, the configuration of each peershould also be changed accordingly. IBGP peer and EBGP peer can not be in the samegroup.

Table RC-7-7 Configure a BGP neighbor to be a member of a peer group

Operation Command

Configure a BGP neighbor to be a member of apeer group neighbor neighbor-address peer-group group-name

Delete a BGP neighbor to be a member of a peergroup no neighbor neighbor-address peer –group group-name

By default, there is no BGP neighbor in a peer group.

II. Add an Entry to the BGP Neighbor Table

Table RC-7-8 Add an entry to the BGP neighbor table

Operation Command

Add an entry to the BGP neighbor table neighbor neighbor-address remote-as as-numberRemove an entry to the BGP neighbor table no neighbor neighbor-address remote-as as-number

By default, there is no BGP neighbor peers.

III. Accept an Attempt BGP Connections to External Peers Residing onNetworks that are not Directly Connected

Table RC-7-9 Accept an attempt BGP connections to external peers residing on networks that are notdirectly connected

Operation Command



7-7

Accept an attempt BGP connections to external peersresiding on networks that are not directly connected neighbor neighbor-address ebgp-multihop [ ttl ]Return to the default BGP connections to external peers no neighbor neighbor-address ebgp-multihop

By default, only directly connected neighbors are allowed to be connected

IV. Set the Timers for a Specific BGP Peer

Table RC-7-10 Set the timers for a specific BGP peer

Operation Command

Set the timers for a specific BGP peer neighbor neighbor-address timers keepalive-intervalholdtime-interval

Clear the timers for a specific BGP peer no neighbor neighbor-address timers

By default, the value of keepalive-interval is 60 seconds, the value of holdtime-intervalis 180 seconds.

Caution: The timer configured with this command is of higher preference than thatconfigured with timer bgp command.

V. Set the Minimum Interval between the Sending of BGP Routing Updates

Table RC-7-11 Set the minimum interval between the sending of BGP routing updates

Operation Command

Set the minimum interval between the sending ofBGP routing updates

neighbor neighbor-address advertisement-intervalseconds

Restore the minimum interval between the sendingof BGP routing updates to its default value

no neighborneighbor-address advertisement-interval

By default, the interval between the sending of BGP routing updates is 5 seconds.

VI. Specify that a Communities Attribute should be Sent to a BGP Neighbor

Table RC-7-12 Specify that a communities attribute should be sent to a BGP neighbor

Operation Command

Specify that a communities attribute should be sent toa BGP neighbor neighbor neighbor-address send-community

Remove that a communities attribute should be sentto a BGP neighbor no neighbor neighbor-address send-community

By default, no communities attribute is sent to any neighbor.

VII. Configure the Router as a BGP Route Reflector and Configure theSpecified Neighbor as its Client

Table RC-7-13 Configure the router as a BGP route reflector and configure the specified neighbor as itsclient



7-8

Operation Command

Configure the router as a BGP route reflectorand configure the specified neighbor as its client neighbor neighbor-address route-reflector-client

Indicate that the neighbor is not a client no neighbor neighbor-address route-reflector-client

By default, there is no route reflector in the autonomous system.

VIII. Allow a BGP Speaker to Send the Default Route 0.0.0.0 to a Neighbor

Table RC-7-14 Allow a BGP speaker to send the default route 0.0.0.0 to a neighbor

Operation Command

Allow a BGP speaker to send the default route0.0.0.0 to a neighbor for use as a default route neighbor neighbor-address default-originate

Send no route as a default no neighbor group-name default originate

By default, no default route is sent to the neighbor, a next hop should be sent to thepeer unconditionally as the default route.

IX. Disable Next-hop Processing of BGP Updates on the Router

Disable BGP processing of next hop when sending a route to the peer and take theself-address as the next hop.

Table RC-7-15 Disable next-hop processing of BGP updates on the router

Operation Command

Disable next-hop processing of BGP updates on the router neighbor neighbor-address next-hop-self

Enable next-hop processing of BGP updates on the router no neighbor neighbor-address next-hop-self

By default, next-hop processing of BGP updates on the router is disabled.

X. Apply a Route Map to Incoming or Outgoing Routes

Table RC-7-16 Apply a route map to incoming or outgoing routes

Operation Command

Apply a route map to incoming or outgoing routes neighbor neighbor-address route-map map-name{ in | out }

Remove a route map to incoming or outing routes no neighbor neighbor-address route-map map-name { in | out }

By default, no route maps are applied to a peer.

XI. Filter BGP Routing Updates to/from Neighbors as Specified in an Access-list

Table RC-7-17 Filter BGP routing updates to/from neighbors as specified in an access-list



7-9

Operation Command

Filter BGP routing updates to/from neighborsas specified in an access-list

neighbor neighbor-address distribute-list access-list-number { in | out }

Remove Filter BGP routing updates to/fromneighbors as specified in an access-list

no neighbor neighbor-address distribute-list access-list-number { in | out }

By default, no BGP neighbor is specified.

XII. Establish a BGP Filter

Table RC-7-18 Establish a BGP filter

Operation Command

Establish a BGP filter neighbor neighbor-address filter-list aspath-list-number { in | out }Disable a BGP filter no neighbor neighbor-address filter-list aspath-list-number { in | out }

By default, a BGP filter is disabled.

XIII. Configure the BGP Version

Table RC-7-19 Configure the BGP version

Operation Command

Configure the software to accept only a particularBGP version neighbor neighbor-address version version-number

Use the default version level of a peer group no neighbor neighbor-addres version

By default, software accepts BGP Version 4.

7.2.9 Configure BGP Peer Groups

Using BGP peer group can facilitate user configuration. When starting several peers ofthe same configuration, you can first create and configure one peer group, then addother peer groups into this group to get the same configuration. Note: configure thepeer group under the guidance of professionals.

Perform the following peer group configuration in BGP protocol configuration mode.

I. Create a Peer Group

By default, IBGP peer will be added to the default peer group and no configuration isnecessary. The configuration of route updating strategy to any IBGP peer is onlyeffective to other IBGP peers in the group. If the router is not a route reflector, all IBGPpeers are in one group. If the router is a route reflector, all route reflection clients are inone group and non-clients are in another group.

The members of external peer group must be in the same network segment, otherwisesome EBGP peers may discard the route updating information you have sent.

If the peer group is not configured with AS number, all peers in this group must beconfigured with AS numbers of their own. If the peer group is configured with AS



7-10

number, any peer in this group can not be configured with an AS number which is thesame as a peer in another group.

The members of the peer group can not be configured with a route updating strategydifferent from that of the group but different access strategy is permitted.



7-11

Table RC-7-20 Create a peer group

Operation Command

Create a peer group neighbor group-name peer-groupRemove the peer group and all of its members no neighbor group-name peer-groupReset the connection of all members in the peer group clear ip bgp peer-group group-name

By default, there is no BGP peer group.

II. Add an Entry to the BGP Peer Group Table

Table RC-7-21 Add an entry to the BGP peer group table

Operation Command

Add an entry to the BGP peer group table neighbor group-name remote-as as-numberRemove an entry to the BGP peer group table no neighbor group-name remote-as as-number

By default, there is no BGP peer group.

III. Accept an Attempt BGP Connections to External Peer Group Residing onNetworks that are not Directly Connected

Table RC-7-22 Accept an attempt BGP connections to external peer group residing on networks that arenot directly connected

Operation Command

Accept an attempt BGP connections to external peer groupresiding on networks that are not directly connected neighbor group-name ebgp-multihop [ ttl ]Return to the default BGP connections to external peer group no neighbor group-name ebgp-multihop

By default, only directly connected neighbors are allowed to be connected

ttl is the maximum hop value. The default value is 64, ranging from 1 to 255.

IV. Set the Timers for a Specific BGP Peer Group

Table RC-7-23 Set the timers for a specific BGP peer group

Operation Command

Set the timers for a specific BGP peer group neighbor group-name timers keepalive-intervalholdtime-interval

Clear the timers for a specific BGP peer group no neighbor group-name timers

By default, the value of keepalive-interval is 60 seconds, the value of holdtime-intervalis 180 seconds.

Note that the timers configured with this command is of higher preference than thevalues configured with timer bgp command.



7-12

V. Set the Minimum Interval between the Sending of BGP Routing Updates

Table RC-7-24 Set the minimum interval between the sending of BGP routing updates

Operation Command

Set the minimum interval between the sending ofBGP routing updates neighbor group-name advertisement-interval seconds

Restore the minimum interval between the sendingof BGP routing updates to its default value no neighbor group-name advertisement-interval

By default, the interval between the sending of BGP routing updates is 5 seconds

VI. Specify that a Communities Attribute should be Sent to a BGP Peer Group

Table RC-7-25 Specify that a communities attribute should be sent to a BGP peer group

Operation Command

Specify that a communities attribute should be sent to aBGP peer group neighbor group-name send-community

Remove that a communities attribute should be sent to aBGP peer group no neighbor group-name send-community

By default, no communities attribute is sent to any peer group.

VII. Configure the Router as a BGP Route Reflector and Configure theSpecified Peer Group as its Client

By default, all IBGP in the autonomous system must be fully connected and a neighborno long advertises the route received from the IBGP neighbor, in order to prevent routeloop. However, if the route reflector is used, all IBGP speakers are not necessary to befully connected. In the route reflector model, internal BGP peer is configured to a routereflector, engaged in transmitting to IBGP the existing route to IBGP neighbor. Thisdesign eliminates the demand of communication between each router. Configure thelocal router to route reflector with neighbor route-reflector-client command andconfigure the specified neighbor to one of its clients. All configured neighbors areregarded as the members of the client group. The rest IBGP peers will be members ofnon-client group of the local route reflector.

Generally, it is unnecessary to configure this command for peer group because IBGPneighbors are in default group. You can configure the route reflector client with thecommand neighbor neighbor-address route-reflector-client. This command isreserved for compatibility with Cisco routers.

Table RC-7-25 Configure the router as a BGP route reflector and configure the specified peer group as itsclient

Operation Command

Configure the router as a BGP route reflector andconfigure the specified peer group as its client neighbor group-name route-reflector-client

Indicate that the peer group is not a client no neighbor group-name route-reflector-client



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By default, there is no route reflector in the autonomous system.

VIII. Allow a BGP Speaker to Send the Default Route 0.0.0.0 to a Peer Group

Table RC-7-26 Allow a BGP speaker to send the default route 0.0.0.0 to a peer group

Operation Command

Allow a BGP speaker to send the default route 0.0.0.0 to apeer group neighbor group-name default-originate

Send no route as a default no neighbor group-name default-originate

By default, no default route is sent to the peer group, a next hop should be sent to thepeer unconditionally as the default route.

IX. Disable Next-hop Processing of BGP Updates on the Router

Cancel the processing of next hop when sending a route to the peer and take theself-address as the next hop.

Table RC-7-27 Disable next-hop processing of BGP updates on the router

Operation Command

Disable next-hop processing of BGP updates on the router neighbor group-name next-hop-selfEnable next-hop processing of BGP updates on the router no neighbor group-name next-hop-self

By default, next-hop processing of BGP updates on the router is disabled.

X. Apply a Route Map to Incoming or Outgoing Routes

Table RC-7-28 Apply a route map to incoming or outgoing routes

Operation Command

Apply a route map to incoming or outgoing routes neighbor group-name route-map map-name { in | out }Remove a route map to incoming or outing routes no neighbor group-name route-map map-name { in | out }

By default, no route maps are applied to a peer group.

XI. Filter BGP Routing Updates to/from Peer group as Specified in an Access-list

Table RC-7-29 Filter BGP routing updates to/from peer group as specified in an access-list

Operation Command

Filter BGP routing updates to/from peergroup as specified in an access-list

neighbor group-name distribute-list access-list-number { in |out }

Remove Filter BGP routing updates to/frompeer group as specified in an access-list

no neighbor group-name distribute-list access-list-number { in| out }



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By default, no BGP peer group is specified.

XII. Establish a BGP Filter

Table RC-7-30 Establish a BGP filter

Operation Command

Establish a BGP filter neighbor group-name filter-list aspath-list-number { in | out }Remove a BGP filter no neighbor group-name filter-list aspath-list-number { in | out }

By default, a BGP filter is disabled.

XIII. Configure the BGP Version

Table RC-7-31 Configure the BGP version

Operation Command

Configure the software to accept only a particular BGP version neighbor group-name version version-numberUse the default version level of a peer group no neighbor group-name version

By default, software accepts BGP Version 4.

7.2.10 Create an Aggregate Addresses

CIDR supports manual route aggregation. Manual aggregation of aggregate-addressis the aggregation of BGP local route. The parameters can be set at the same timewhen manual aggregation mode is configured.


Table RC-7-32 Create an aggregate addresses

Operation Command

Create an aggregate entry in a BGProuting table

aggregate-address address mask [ as-set ] [ summary-only][ suppress-map map-name ] [ advertise-map map-name ][ attribute-map map-name ]

Disable an aggregate entry in a BGProuting table

no aggregate-address address mask [ as-set ] [ summary-only][ suppress-map map-name ] [ advertise-map map-name ][ attribute-map map-name ]

By default, an aggregate is disabled.

7.2.11 Configure a Route Reflector

To guarantee the connectivity between the IBGP peers, an all-closed network shallexist between IBGP peers. In some networks, the internal BGP network may becomevery large (with more than one hundred sessions in each router), resulting in hugeoverhead. The basic concept of the route reflector is that the route reflector designatesa central router as the core of the internal sessions. Multiple BGP routers can peer withthis central router, and then multiple route reflectors can peer each other.



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Since the route reflector is the center of other routers, other routers are called clientrouters from the viewpoint of the reflector. The client routers peer the route reflector andexchange routing information. The route reflector will forward (reflect) informationamong the client routers in turn.

As shown in the following diagram, Router A receives an update from an external peerand transfers it to Router B. Router B is configured as a route reflector, which has twoclients: Router A and Router C.

Router B can reflect the routing update from client Router A to client Router C. In thisinstance, the session between Router A and Router C is unnecessary because theroute reflector will forward the BGP information to Router C.

Router

EBGPEBGP

Route Reflector Reflected router

Update route

Router B

Router A Router C

Figure RC-7-1 Schematic diagram of route Reflector

A route reflector divides IBGP peers into clients and non-clients. A route reflector andits clients form a Cluster. All other peers of the route reflector that do not belong to thiscluster are called non-clients.

The non-clients must form an all-closed network with the reflector, as they follow thebasic rules of IBGP. And a client should not be peer of other internal speakers outsideits cluster. The reflecting function is achieved only on the route reflector, all the clientsand non-clients are normal BGP peers irrelevant to the function. A client is a client onlybecause the route reflector regards it as the client.

When the router reflector received several routes to one destination, it will choose thebest one based on usual BGP routing strategy process. The best route transfers insideAS according to following rules:

If the route is received from non-client peers, it only reflects to clients.

If the route is received from client peers, it reflects to all of the clients and non-clientsexcept this route’s sender.

If the route is received by EBGP peer, it reflects to all clients and non-clients peers thatcan be reflected.

I. Restore Route Reflection from a BGP Route Reflector to Clients




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Table RC-7-33 Restore route reflection from a BGP route reflector to clients

Operation Command

Enable client-to-client route reflection bgp client-to-client reflectionDisable client-to-client route reflection no bgp client-to-client reflection

If the clients are already fully connected, the configured client-to-client reflector will notwork. By default, the clients of the route reflector are not required to be fully connected.After configuring a route reflector, it will reflect the route of one client to all other clients.

II. Configure the Cluster ID

As the route reflector is redistributed, the route selection circle may occur in an AS, andthe route update leaving a cluster may try to reenter this cluster. The traditional ASrouting method can not detect the internal circle of the AS, because the update has notleft the AS yet. BGP provides two methods to avoid AS internal loop when youconfigure the route reflector:

1) Configure originator-ID of the route reflector:

Originator-ID is a 4-bit, optional, non-transitional BGP attribute created by routereflector. It carries the router ID of the originator of the route in the local AS. If theconfiguration is improper, and the routing update returns to the originator, the originatorwill discard it.

You don’t need to configure this parameter, and it will function automatically when BGPprotocol is started.

2) Configure cluster-ID of the route reflector:

Usually, there is only one route reflector in a cluster, which is tagged with router ID ofthe route reflector.

To increase redundancy and prevent single-point fault, there can be more than oneroute reflectors. They are mutually redundant and configured as the non-client of theother. Then all route reflectors in the cluster must be tagged with a 4-byte cluster ID, soas to identify the routing update from other route reflectors in the same cluster. If thereis more than one route reflector in the cluster, the same cluster ID should be configuredto all route reflectors.


Table RC-7-34 Configure the Cluster ID

Operation Command

Configure the cluster ID if the BGP has more than one route reflector bgp cluster-id cluster-idRemove the cluster ID no bgp cluster-id cluster-id

By default, the router ID of the single route reflector in a cluster.

7.2.12 Create a Community List for BGP

In BGP range, a community is a group of destinations with common characters. Acommunity is not limited to a network or an AS, and has no physical boundary.



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Community attribute is an optional and transitional attribute. Some communities arecommonly recognized and globally functional. These communities are called standardcommunities. Sometimes the extended community attribute can be defined for specialpurposes.

Community attribute list is used to identify the community information. It can be astandard-community-list and an extended-community-list.

In addition, one route can have more than one community attribute. The speaker withmultiple community attributes in a route can work according to one, several or allattributes. The community attribute can be added or modified before the routertransfers a route to other peers.


Table RC-7-35 Create a Community List for BGP

Operation Command

Create a standard-community-list ip community-list standard-community-list-number { permit |deny } { aa:nn | internet | local-AS | no-advertise | no-export }

Create an extended-community-list ip community-list extended-community-list-number { permit |deny } as-regular-expression

Delete the specified community list no ip community-list {standard-community-list-number | extended-community-list-number }

By default, no community list is created.

7.2.13 Configure a BGP Routing Domain Confederation

Confederation is another method to solve the problem of sudden increase of IBGPclosed networks inside AS. An AS is divided into multiple sub-ASs and the IBGP peersinside the sub-ASs are fully connected, and each sub-AS connects with other sub-ASsinside the confederation. Although the peers in the sub-AS conduct EBGP sessions,they exchange routing information like IBGP peers. And important information such asnext hop, MED value and local preference will not be lost when passing through thesub-AS.

The setback is that when non-confederation scheme changes to confederation scheme,it’s required reconfigure the router and modify the logic topology. In addition, if BGPstrategy is not manually configured, the best path may not be selected through theconfederation.

I. Configure a BGP Confederation

A method to reduce IBGP full connections is dividing an AS into multiple ASs and groupthem into a confederation. Each AS is fully connected internally. Although the peersbetween different sub-AS conduct EBGP sessions, they can exchange routinginformation like IBGP peers. Especially, important information such as next hop, MEDvalue and local preference will not be lost when passing the sub-AS.

You can use different IGP for each sub-AS. Externally, a sub-AS is an integer andconfederation ID is the identification of the sub-AS.




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Table RC-7-36 Configure a BGP Confederation

Operation Command

Specify a BGP confederation identifier bgp confederation identifier as-numberRemove a BGP confederation identifier no bgp confederation identifier

By default, no confederation identifier is configured.

II. Specify the AS that Belong to a Confederation

The configured sub-AS is inside a confederation and each sub-AS uses fully closednetwork. Use bgp confederation identifier command to specify the confederation IDof the AS. If the confederation ID is not configured, this configuration item is invalid.


Table RC-7-37 Specify the AS that Belong to a Confederation

Operation Command

Specify the AS that belong to a confederation bgp confederation peers as-number [ as-number ]Remove an AS from the confederation no bgp confederation peers as-number [ as-number ]

By default, no confederation peers are specified.

III. Configure the AS that Belong to the Confederation Compatible with Cisco

Since the AS confederation of Cisco is different from RFC1965, you shall configure therouters in the confederation in order to inter-work with Cisco routers.


Table RC-7-38 Configure the AS that Belong to the Confederation Compatible with Cisco

Operation Command

Configure the AS that belong to the confederation compatiblewith Cisco bgp confederation cisco-compatible

Cancel the AS that belong to the confederation compatiblewith Cisco no bgp confederation cisco-compatible

By default, the AS that belong to the confederation is in compliant with RFC1965, andincompatible with Cisco routers.

7.2.14 Configure Route Dampening

Route instability mainly indicates that a route used to exist in the routing tabledisappears. This route may reappear and disappear frequently, which is called RoutingFlapping. When there is a flapping, the UPDATE and WITHDRAWN messages will bebroadcast repeatedly over the network, occupying a lot of bandwidths and processingtime of the routers. The administrator should try to avoid it. Route dampening is atechnology to control Routing Flapping.



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Routes conclude stable routes and unstable routes. Stable routes will stay at routetable continuously, while unstable routes should be suppressed by route dampeningThe unstable route will be given a penalty, it won’t be advertised when the penaltyreaches a threshold. The penalty will be exponentially decreased as time goes by.Once it is lower than a certain threshold, the route is unsuppressed and will beadvertised again.

As shown in the following diagram:

Suppression threshold

Threshold to reuse

Time

Penalty

Figure RC-7-2 Schematic diagram of route dampening

Configure the following parameters to adjust the performance of route dampening:

l Penalty: increases upon each route flap, decays as time goes by;

l Reachable-half-life: time duration before the penalty of reachable route reduced to

half;l Unreachable-half-time: time duration before the penalty of unreachable route

reduced to half;

l Ceiling-max-suppress: the maximum value of penalty;

l Suppress-limit: the route advertisement is suppressed when the penalty reaches

this threshold;l Reuse-limit: the route advertisement is unsuppressed when the penalty is lower

than the value;

I. Configure Route Dampening


Table RC-7-39 Configure Route Dampening

Operation Command

Enable route dampening or changevarious BGP route dampening factors

bgp dampening [ half-life-reachable half-life-unreachable reusesuppress ceiling ] [ route-map map-name ]

Clear route routing dampening informationand de-suppress the suppressed route clear ip bgp dampening [ network-address [ mask ] ]Disable the route dampening no bgp dampening



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By default, no route dampening is enabled.

The parameters are mutually dependent. To configure any parameter, all otherparameters should also be specified.

II. Monitor Route Flap Information

Perform the following task in privileged configuration mode.



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Table RC-7-40 Monitor Route Flap Information

Operation Command

Show dampened route information show ip bgp dampened-pathsShow flap statistics of all routes information show ip bgp flap-statisticsShow the route flap statistics of routes with AS pathcomply with regular expression show ip bgp flap-statistics regexp as-regular-expression

Clear BGP flap statistics that match the regularexpression

clear ip bgp flap-statistics regexp [ as-regular-expression ]

Show the route flap statistics of routes that passedAS filter-list show ip bgp flap-statistics filter-list aspath-list-number

Clear BGP flap statistics that pass the filter list clear ip bgp flap-statistics filter-list [ aspath-list-number ]Show the route flap statistics of routes withdesignated destination address

show ip bgp flap-statistics network-address mask[ longer-prefixes ]

Clear the route flap statistics of routes withdesignated destination address clear ip bgp flap-statistics network-address

Clear the route flap statistics of routes receivedfrom the specified neighbor.

clear ip bgp network-address flap-statistics [ longer-prefixes ]

7.2.15 Configure Synchronization of BGP and an IGP

BGP protocol prescribes that a BGP router will not advertise the destination knownthrough internal BGP peers to external peers, unless the destination can be known alsothrough IGP. If a router can know the destination through IGP, then the route can bedistributed in AS because internal connect has been ensured.

One major task of BGP protocol is to distribute the network reachable information of thelocal AS to other ASs. Therefore, BGP needs to distribute the route information bysynchronization with IGP (such as RIP and OSPF), Synchronization means that BGPcannot distribute transition information to other ASs until IGP broadcasts the routeinformation successfully in its AS. That is to say, before a router received an updateddestination information from IBGP peer and advertised it to other EBGP peers, it will tryto check whether this destination can be reached through AS.


Table RC-7-41 Configure Synchronization of BGP and an IGP

Operation Command

Enable the synchronization between BGP an IGP synchronizationDisable the synchronization between BGP an IGP no synchronization

By default, the synchronization between BGP an IGP is enabled.

Quidway series routers provide ”Cancel BGP and IGP synchronization” option in orderthat the synchronization between BGP and IGP can be cancelled and the route fromIBGP can be distributed without reconsidering if the IGP route still exists.

The synchronization of border router can be shutdown safely in the following cases:

l All the routers of AS can form a IBGP totally-closed network. In such a case, a

route known from any border router’s EBGP can be automatically transferred to

any other router through IBGP so that the connection of AS is ensured.

l When AS is not a transitional AS.



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7.2.16 Configure the Interaction between BGP and an IGP

I. Configure Route Redistribution for BGP

BGP can import route information that is found by running IGP in other AS to its ownAS.


Table RC-7-42 Configure Route Redistribution for BGP

Operation Command

Configure route redistribution for BGP redistribute protocol [ metric metric ] [ route-map map-name ]Cancel route distribution for BGP no redistribute protocol

By default, BGP does not redistribute routes from other domain into the routing table.

protocol specifies the source routing domain that can be redistributed. At present, ripcan redistribute routes domain such as connected, static, rip, igrp, eigrp, ospf andospf-ase.


II. Allow the Redistribution of Network 0.0.0.0 into BGP

redistribute command can not redistribute default route into BGP, please usedefault-information originate command to redistribute the default route into BGP.


Table RC-7-43 Allow the Redistribution of network 0.0.0.0 into BGP

Operation Command

Allow the redistribution of network 0.0.0.0 into BGP default-information originateDisable the redistribution of network 0.0.0.0 into BGP no default-information originate

By default, the redistribution of network 0.0.0.0 into BGP is disabled.

7.2.17 Define an Access-list Entry, an AS Path-list Entry, a Route-Map

This section describes the configuration of access list, AS path list and route-map.

I. Define an Access-list Entry

Refer to “3.4.3 Configuring Access Control List” part 5 “Security Configuration” of themanual.



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II. Define a BGP-related Access-list Entry

There is an AS path field in the routing information packet of BGP protocol. When BGPprotocol is switching routing information, the path of the routing information crossingthe AS will be recorded in this field. aspath-list is identified with as-number. Whendefining aspath-list, you can specify an aspath regular expression used to match theaspath field in the routing information. Use aspath-list to match the aspath field in theBGP routing information, filtering the information not meeting the conditions. The usercan define multiple aspath-lists for one list number, i.e. one list number represents agroup of aspath-lists. Each AS path list is identified with numbers.


Table RC-7-44 Define a BGP-related Access-list Entry

Operation Command

Define a BGP-related access-list ip as-path access-list aspath-list-number { permit | deny } as-regular-expression

Remove a BGP-related access-list no ip as-path access-list aspath-list-number

By default, no access list entry is defined.

In the matching process, many access-list-number are of “OR” relationship, i.e. if therouting information passes one item, information will be filtered by the as-path listidentified with this list number.

III. Define a Route-map

Route-map is an important part for BGP to implement route strategy. According to thematching result of the route attribute, it decides the operation on route attribute, i.e.modifying the attribute of route set of the specific condition. In each route map therecan be several mapping rules, labeled with serial number. In route mapping, matchfrom small serial number to big ones. When finding the first matched map rule, thisprocess is completed. If no matched map rules are found, router receiving andtransmitting will be canceled.


Table RC-7-45 Define a Route-map

Operation Command

Define a route-map and enter into the Route-mapconfiguration mode route-map map-name { permit | deny } [ seq-number ]Remove a specified route-map no route-map map-name [ permit | deny ] [seq-number ]

By default, no route-map is defined.

IV. Define a Match Rules

Perform the following task in BGP route-map configuration mode.



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Table RC-7-46 Define a Match Rules

Operation Command

Match a BGP AS path access list match as-path aspath-list-numberDelete a BGP AS path access list no match as-path aspath-list-number

Match a BGP community listmatch community-list {standard-community-list-number [ exact-match ] | extended-community-list-number }

Delete BGP community list no match community-list

Match a standard access list or a prefix list match ip address { access-list-number | prefix-listprefix-list-name }

Remove a standard access list or a prefix list no match ip address [ prefix-list ]Match the specified next-hop route out an interface match interface [ type number ]Remove the specified next-hop route out an interface no match interfaceMatch a next-hop router address passed by anaccess list or an prefix list specified

match ip next-hop { access-list-number | prefix-listprefix-list-name }

Remove a next-hop router address passed by anaccess list or an prefix list specified match ip next-hop [ prefix-list ]Match the specified metric match metric metricDelete the specified metric no match metric

By default, AS regular expression, community list, interface type, IP address range andmetric value are not matched.

Refer to “8.2.3 Define Match Clause of Route-Map” for details.

V. Define a Set Clause

Perform the following task in Route-map configuration mode.

Table RC-7-47 Define a Set Clause

Operation Command

Set the BGP AS path access list set as-path aspath-list-numberDelete the BGP AS path access list no set as-path

Set the communities attributes set community { aa:nn | local-AS | no-advertise |no-export } [ additive] | none }

Delete the communities attributes no set communitySpecify the address of the next hop set ip next-hop ip-addressDelete the address of the next hop no set ip next-hopAssign a value to a local BGP path set local-preference valueRestore the value to a local BGP path to its default value no set local-preferenceSet the metric value to give the redistributed routes(forany protocol except IGRP or EIGRP) set metric metric

Set the metric value to give the redistributed routes( forIGRP or EIGRP only) set metric k1 k2 k3 k4 k5

Restore the metric to their default value no set metricSet the BGP origin code set origin { igp | egp as-number | incomplete }Remove the origin code no set origin

By default, AS serial number, BGP community attribute, next hop, local preference,metric value and origin attributes are not set.

Refer to “8.2.4 Define Set Clause of Route-map” for details.



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7.2.18 Configure Route Filter for BGP


1) Configure Filtering Route Information Received by BGP

Table RC-7-48 Filter Routing Information Received by BGP

Operation Command

Filter routing information received from a specifiedgateway distribute-list gateway prefix-list-name in

Change or cancel filtering the routing informationreceived from a specified gateway no distribute-list gateway prefix-list-name in

Filter the routing information received distribute-list { access-list-number | prefix-list prefix-list-name } in

Change or cancel filtering routing informationreceived

no distribute-list { access-list-number | prefix-listprefix-list-name } in

2) Configure Filtering Route Information being Advertised by BGP

Table RC-7-49 Filter Routing Information being Advertised by BGP

Operation Command

Filter routing information being advertised by BGP distribute-list {access-list-number | prefix-listprefix-list-name } out [ protocol ]

Cancel filtering routing information being advertisedby BGP

no distribute-list {access-list-number | prefix-listprefix-list-name } out [ protocol ]

By default, BGP does not filter any route information received or being advertised.

protocol specifies the routing domain that can will be filtered. At present, igrp can filterroutes domain such as connected, static, igrp, eigrp, ospf and ospf-ase.


7.2.19 Reset BGP Connections

After modifying BGP configuration, the user must turn off the current BGP connectionsand reset BGP connections to make the new configuration effective.

Perform the following task in privileged user configuration mode.

Table RC-7-50 Reset BGP Connections

Operation Command

Reset a particular BGP connection clear ip bgp ip-addressReset all BGP connections clear ip bgp *



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7.3 Monitoring and Maintenance of BGP

Table RC-7-51 Monitoring and maintenance of BGP

Operation Command

Show the routing information of the specified IP addressin the routing table. show ip bgp A.B.C.D

Show BGP routing information show ip bgpShow AS filtered path information in BGP show ip as-path access-list-numberShow CIDR route show ip bgp cidr

Show routing information of the specified BGPcommunity

show ip bgp community {aa:nn | internet |local-AS | no-advertise | no-export} [exact-match]

Show routing information of permitted in the specifiedBGP community list

show ip bgp community-list community-list-number [exact-match]

Show BGP dampening route show ip bgp dampened-pathsShow the route matching the specified access-list show ip bgp filter-list access-list-number

Show route flap statisticsshow ip bgp flap-statistics [{ regrexp as-regular-rexpession } | { filter-list list-number } |{address [mask [longer-prefix-list ] ] } ]

Show the route with inconsistent source AS show ip bgp inconsistent-asShow peer information show ip bgp neighbors [ neighbor-address ]Show routing information distributed through BGP show ip bgp networkShow AS path information show ip bgp paths as-regular-expressionShow peer group information show ip bgp peer-group [ group-name ]Show matching AS path information of AS regularexpression show ip bgp regexp as-regular-expression

Show BGP route summary information show ip bgp summaryShow the configured route-map information show route-map map-nameShow BGP event information debug ip bgp

1) Show routing information of the specified IP address in the routing table

Quidway(config)# show ip bgp 14.1.0.0

BGP routing table entry for 14.1.0.0/16

Nexthop : 10.110.156.30

Paths : 600 700 i, metric 1000, valid, external, best

Community: 100:1

2) Show BGP routing information

Quidway(config)# show ip bgp

BGP local router ID is 133.1.1.1

Status codes: s suppressed, d damped, h history, * valid, > best,

i internal

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Path

*> 14.1.0.0/16 10.110.156.30 1000 600 700 i

*> 14.2.0.0/16 10.110.25.20 700 i

* 10.110.156.30 1000 600 700 i

*> 14.3.0.0/16 10.110.25.20 700 i



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* 10.110.156.30 1000 600 700 i

*> 14.4.0.0/16 10.110.25.20 700 i

* 10.110.156.30 1000 600 700 i

*> 14.5.0.0/16 10.110.156.30 1000 600 700 i

*> 112.1.0.0/16 0.0.0.0 i

*> 133.1.1.0/24 0.0.0.0 i

3) specified BGP community

Quidway(config)# show ip bgp community 600:1

Routing Tables:

Destination/Mask Pref Nexthop Interface Metric Path

3.1.0.0/16 170 10.110.156.30 Ethernet0 0/0 600 700 i

13.2.0.0/16 170 10.110.156.30 Ethernet0 0/0 600 700 i

13.3.0.0/16 170 10.110.156.30 Ethernet0 0/0 600 700 i

13.4.0.0/16 170 10.110.156.30 Ethernet0 0/0 600 700 i

13.5.0.0/16 170 10.110.156.30 Ethernet0 0/0 600 700 i

4) Show peer group information

Quidway(config)# show ip bgp peer my_peer

peer-group: my_peer no remote-as still

configuration within the peer-group :

no export policy routemap

no export policy distribute list

no export policy filter list

routemap specified in import policy : map1

no import policy distribute list

no import policy filter list

peer-group can't generate default route

5) Show BGP route summary information

Quidway(config)# show ip bgp summary

Neighbor V AS MsgRcvd MsgSent OutQ Up/Down State

10.110.156.30 4 600 3 6 0 00:01:06 Established

10.110.25.21 4 700 0 0 0 00:00:42 Active

10.110.25.20 4 700 14 20 0 00:11:35 Established

7.4 Typical Configuration of BGP

7.4.1 Configuring AS Confederation Attribute


As shown in the following diagram, AS 100 is divided into 3 sub-ASs: 1001, 1002, 1003,which are configured with EBGP, confederation EBGP and IBGP.



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AS200

AS100

AS1002AS1001

AS1003

Ethernet172.68.10.1 172.68.10.2

172.68.10.3

172.68.1.2

172.68.1.1

156.10.1.1

156.10.1.2

Router A Router B

Router C Router D

Router E

Figure RC-7-3 Networking diagram of configuring AS confederation



RouterA(config)# router bgp 1001

RouterA(config-router-bgp)# bgp confederation identifier 100

RouterA(config-router-bgp)# bgp confederation peers 1002 1003

RouterA(config-router-bgp)# neighbor 172.68.10.2 remote-as 1002



RouterB(config)# router bgp 1002

RouterB(config-router-bgp)# bgp confederation identifier 100

RouterB(config-router-bgp)# bgp confederation peers 1001 1003

RouterB(config-router-bgp)# neighbor 172.68.10.1 remote-as 1001



RouterC(config)# router bgp 1003

RouterC(config-router-bgp)# bgp confederation identifier 100



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RouterC(config-router-bgp)# bgp confederation peers 1001 1002

RouterC(config-router-bgp)# neighbor 172.68.10.1 remote-as 1001




7.4.2 Configuring BGP Route Reflector


Router B receives a BGP update message and forwards the update to Router C, whichis configured as a route reflector and has two clients: Router B and Router D. WhenRouter C receives routing update from Router B, it reflects the information to Router D.Therefore, IBGP connection is not necessary between Router B and Router D,because Router C will reflect the information to Router D.


IBGP IBGPEBGP

Route reflector client

Route reflectorS1

194.1.1.1/24S0

193.1.1.1/24

S1 193.1.1.2/24S0194.1.1.2/24S0192.1.1.2/24

S0192.1.1.1/24 2.2.2.2 4.4.4.4

1.1.1.1

3.3.3.3

AS100

AS200

Connected with network 1.0.0.0

S1

Router C

Router B Router DRouter A

Route reflector client

Figure RC-7-4 Networking diagram of configuring route reflector








! Configure Serial 0





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RouterB(config-router-ospf)# network 193.1.1.0 0.0.0.255 area 0

! Configure peer and route reflector












RouterC(config-router-ospf)# network 194.1.1 0 0.0.0.255 area 0

! Configure BGP peer


RouterC(config-router-bgp)# neighbor 193.1.1.2 remote as 200 route-reflector-client

RouterC(config-router-bgp)# neighbor 194.1.1.2 remote as 200 route-reflector-client






RouterD(config-router-ospf)# network 194.1.1.0 0.0.0.255 area 0

! Configure BGP peer

RouterD(config)# router bgp 200

RouterD(config-router-bgp)# neighbor 194.1.1.1 remote as 200

View BGP routing table on Router B with show ip bgp command. Note: Router Bknows that network 1.0.0.0 exists.

RouterB# show ip bgp



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network next hop metric localpref

1.0.0.0 192.1.1.1 0

View BGP routing table on Router C with show ip bgp command. Note: Router Cknows that network 1.0.0.0 exists.

RouterD# show ip bgp

network next hop metric localpref

1.0.0.0 194.1.1.1 0 100

7.4.3 Configuring BGP Path Selection


This example describes how the administrator manages the routing through BGPattribute. All routers are configured with BGP. OSPF is used by IGP in AS200. Router Ais in AS100, functioning as the BGP neighbor of Router B and Router C in AS200.When Router B and Router C run IBGP to Router D, Router D is also in AS200.


Router B

Router C

Router DRouter A

S0194.1.1.2/24

S0 192.1.1.1/24

S1 193.1.1.1/24

S0 193.1.1.2/24 S1195.1.1.2/24

S0192.1.1.2/24

2.2.2.2

4.4.4.4

3.3.3.3

1.1.1.1

AS100

AS200

S0194.1.1.1/24

S1195.1.1.1/24

IBGP

IBGPEBGP

EBGP1.0.0.0

To network2.0.0.0

2.0.0.0To network

To network

2.0.0.0To network

Figure RC-7-5 Networking diagram of configuring BGP path selection







! Start BGP



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! Specify BGP transmission network

RouterA(config-router-bgp)# network 1.0.0.0

RouterA(config-router-bgp)# network 2.0.0.0

! Configure peer

RouterA(config-router-bgp)# neighbor 192.1.1.2 remote as 200

RouterA(config-router-bgp)# neighbor 193.1.1.2 remote as 200

Configure MED attribute of Router A

l Add access list to Router A and enable network 1.0.0.0.

Router(config)# access-list 1 permit 1.0.0.0 1.0.0.0 0.255.255.255

l Define two routing diagram, namely set_med_50 and set_med_100. The first

routing diagram is network 1.0.0.0, MED attribute is 50 and the second MEDattribute is 100.

RouterA(config)# route-map set_med_50 10

RouterA(config-route-map)# match ip address 1

RouterA(config-route-map)# set metric 50

RouterA(config-route-map)# exit

RouterA(config)# route-map set_med_100 10

RouterA(config-route-map)# match ip address 1

l RouterA(config-route-map)# set metric 100Apply the routing diagram set_med_50

to the exit routing update of Router C (193.1.1.2). Apply the routing diagram

set_med_100 to exit routing update of Router B (192.1.1.2).


RouterA(config-router-bgp)# neighbor 193.1.1.2 route-map set_med_50 out

RouterA(config-router-bgp)# neighbor 192.1.1.2 route-map set_med_100 out










RouterB(config-router-bgp)# no synchronization



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RouterB(config-router-bgp)# neighbor 192.1.1.1.1 remote-as 100





RouterC(config-if-Serial)# ip address 193.1.1.2 255.255.255.0




RouterC(config-router-ospf)# network 193.1.1.0 0.0.0.255 area 0

RouterC(config-router-ospf)# network 195.1.1.0 0.0.0.255 area 0


RouterC(config-router-bgp)# no synchronization

RouterC(config-router-bgp)# neighbor 193.1.1.1 remote as 100



Set the local preference attribute of the Router C.

l Add access list 1 to Router C and enable network 1.0.0.0.

RouterC(config)# access-list 1 permit 1.0.0.0 0.255.255.255

l Define a routing diagram named localpref. In the diagram, the local preference of

the route matching access list 1 is set to 200 and the local preference of the routenot matching access list 1 is 100.

RouterC(config)#route-map localpref 10

RouterC(config-route-map)# match ip address 1

RouterC(config-route-map)# set local perference 200

Router C(config-route-map)# route-map localpref permit 20

RouterC(config-route-map)# set local perference 100

l Apply this routing diagram to the entry traffic from BGP neighbor 193.1.1.2 (Router

A).

RouterC(config)# router bgp200

RouterC(config-router-bgp)# neighbor 193.1.1.1 route-map localpref in







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RouterD(config-router-ospf)#network 194.1.1.0 0.0.0.255 area 0

RouterD(config-router-ospf)#network 195.1.1.0 0.0.0.255 area 0

RouterD(config-router-ospf)# network 4.0.0.0 0.0.0.255 area 0

RouterD(config)# router bgp 200

RouterD(config-router-bgp)# no synchronization

RouterD(config-router-bgp)# neighbor 194.1.1.2 remote-as 100

RouterD(config-router-bgp)# neighbor 194.1.1.2 remote-as 200

To make the configuration effective, use clear ip bgp* command to reset all BGPneighbors.


Chapter 8IP Routing Protocol-Independent Configuration

8-1

Chapter 8 IP Routing Protocol-Independent

Configuration

8.1 Brief Introduction of IP Routing Protocol-IndependentFeatures

During the information exchange with the peer router, the routing protocol might needto receive or distribute only part of the route information compliant with given conditions;and to redistribute only part of the route information learned by other protocols thatsatisfy the preset conditions. In addition, some attributes of the redistributed routeinformation are set in order to satisfy the requirements of the protocol. The routestrategy also provides measures for the routing protocol to implement these functions.

The route strategy consists of a series of rules, classified into three types and used forroute information filtering in route advertisement, route receiving and routeredistribution respectively. Since defining a strategy is similar to defining a group offilters, which is used during receiving or advertising route information, or before theroute information exchange between different protocols, route strategy is also calledroute filtering.

Common filter is the basis of route strategy implementation. The user defines somematching conditions as necessary, which will be referred to when making the routingstrategies. Apply these conditions to different objects such as the destination addressof the routing information, and router address publishing the routing information, toimplement route information filtering.

Routing strategy provides fives filters: route-map, access-list, aspath-list, community-list and prefix-list. They serve as the reference for the protocols to work out routingstrategies. They are described as follows:

1) route-map

It is used to match some attribute of the given routing information and set someattributes of the routing information when the conditions are matched. A route-mapcontains several "match" clauses and "set" clauses. The "match" clauses specify thematching conditions, i.e. match the attribute of the given routing information through thefiltering conditions satisfied by the current route-map. The "set" clauses specify theoperations, i.e. the configuration commands executed when the filtering conditionsspecified by match clauses are satisfied.

2) access-list

It can be divided into Standard Access-list and Extended Access-list. The standard oneis usually used for filtering routing information. When defining an access-list, you needto specify the network segment range of an IP address, to match the destinationnetwork segment address or next hop address of the routing information, filter therouting information not satisfying the conditions. If an extended access-list is used, onlythe source address match field is used to match he destination network segment of therouting information, while the IP address range used to match packet destinationaddress specified in the extended access-list should be ignored.



8-2

The definition and check of access-list has already been achieved in firewallconfiguration. Refer to “access-list” command in firewall configuration.

3) Prefix-list

It functions similarly as access-list, which is not easy to understand when used forrouting information filtering, as it is in the format of packet filtering. prefix-list is moreflexible and comprehensible. When applied to routing information filtering, its matchingobject is the destination address information of the routing information. It can also bedirectly used to the router object (gateway), so that the local routing protocol can onlyreceive the routing information distributed by some specific routers. The addresses ofthese filters must be filtered by prefix-list. In this case, the matching object of prefix-list is the source address of the IP header of the route packet.

A prefix-list is identified with the list name and consists of several parts, withsequence-number specifying the matching order of these parts. In each part, you canspecify a matching range in the form of network prefix. Different parts of differentsequence-numbers are of “OR” relation. That is to say, the routing information matchesdifferent parts in turn. Passing a specific part of prefix-list means passing the filtering ofthis prefix-list.

4) Aspath-list

Aspath-list is only used for BGP protocol. There is an aspath field in the routinginformation packet of BGP protocol. When BGP protocol is switching routinginformation, the path of the routing information crossing the AS will be recorded in thisfield. Aspath-list is identified with aspath-list-number. When defining aspath-list, youcan specify an aspath regular expression to match the aspath field in the routinginformation. You can use aspath-list to match the aspath field in the BGP routinginformation, and filter information not satisfying conditions. Each list number can bedefined with multiple aspath-lists, i.e. one list number represents a group of aspath-lists.In the matching process, access-list-numbers are of “OR” relation, i.e. if passing anyone of the list means the routing information is filtered by the aspath list identified withthis list number.

The definition of access-path-list is implemented in BGP configuration. Refer to “ipas-path” command in BGP protocol configuration.

5) community-list

community-list is only used for BGP protocol. In the routing information packet of BGPprotocol, there is a community attribute field, used to identify a community. Actually, it isa method of grouping according to the destination address where the packets are sent.After grouping, the whole group of routing information should be distributed, received orredistributed. community-list is an access-list based on community information, usedfor BGP protocol. Its matching object is the community field of BGP routing information.

community-list definition is already implemented in BGP configuration, please refer toip community-list command.

8.2 Configuring IP Routing Protocol-Independent

8.2.1 IP Routing Protocol-Independent Configuration Task List

IP Routing Protocol-Independent configuration tasks are listed as follows:

l Define a Route-map

l Define a Matching Rules



8-3

l Defining a Setting Clause

l Redistributing routing information of other protocols

l Define a Prefix-list Entry

l Configure Route Filtering

8.2.2 Define a Route-map

A route-map consists of several parts and each part has its own match clauses and setclauses, with sequence-number specifying the matching order of these parts.


Table RC-8-1 Define a Route-map

Operation Command

Define a route-map and enter into the Route-mapconfiguration mode. route-map map-name { permit | deny } { seq-number }Delete a route-map no route-map map-name [ permit | deny ] [seq-number ]

By default, no route-map is defined.

permit specifies the matching mode of the defined route-map node as permit mode.When the route item satisfies all match clauses of the node, it is permitted to pass thefiltering of this node and execute set clauses of this node. If the route item does notsatisfy the match clauses of this node, the next node of this route-map will be tested.

deny specifies the matching mode of the defined route-map node as deny mode. Whenthe route item satisfies all match clauses of this node, it is rejected to pass the filteringof this node and the next node will not be tested.

Please note that the parts of different seq-number are of “OR” relationship. Namely,route information matches every part in turn. Through a certain part of route-mapmeans filter through this route-map.

8.2.3 Define a Matching Rules

match clause defines matching rules, i.e. meeting the filtering conditions of the routinginformation of the current route-map. The matched objects are the attributes of thisrouting information.

Perform the following task in route-map configuration mode.



8-4

Table RC-8-2 Configure a Matching Rules

Operation Command

Match a BGP AS path access list match as-path aspath-list-numberCancel a BGP AS path access list no match as-path aspath-list-number

Match a BGP community listmatch community-list {standard-community-list-number [ exact-match ] | extended-community-list-number }

Delete a BGP community list no match community-list

Match a standard access list or a prefix list match ip address { access-list-number | prefix-listprefix-list-name }

Delete a standard access list or a prefix list no match ip address [ prefix-list ]Match the specified next-hop route out an interface match interface [ type number ]Remove the specified next-hop route out an interface no match interfaceMatch a next-hop router address passed by an accesslist or an prefix list specified

match ip next-hop { access-list-number | prefix-listprefix-list-name }

Remove a next-hop router address passed by an accesslist or an prefix list specified match ip next-hop [ prefix-list ]Match the specified metric match metric metricRemove the specified metric no match metricMatch the specified OSPF tag value match tag tag-valueDelete the specified OSPF tag value no match tagMatch the specified OSPF route type match route-type { internal | external }Delete the specified OSPF route type no match route-type { internal | external }

By default, AS regular expression, community list, interface type, IP address range,metric value, OSPF tag field and OSPF routing information type are not matched.


1) For one route-map node, the match clauses of the same part are of “AND”

relation in the matching process, i.e. the routing information can not pass the

filtering of route-map unless it passes the matching of all match clauses of this partand it can execute the operation of set sub-clause.

2) If match clause is not specified, all routing information will pass the filtering of this

node.

8.2.4 Define a Setting Clause

set clause specifies operation, i.e. the configuration commands executed after thefiltering conditions specified by match clause are satisfied. The commands are used tomodify some attributes of the routing information.




8-5

Table RC-8-3 Define a Setting Clause

Operation Command

Set the BGP AS path access list set as-path aspath-list-numberDelete the BGP AS path access list no set as-path

Set the communities attributes set community { aa:nn | local-AS | no-advertise | no-export } [ additive ] | none}

Delete the communities attributes no set communitySpecify the address of the next hop set ip next-hop ip-addressDelete the address of the next hop no set ip next-hopAssign a value to a local BGP path set local-preference valueRestore the value to a local BGP path to its default value no set local-preferenceSet the metric value to give the redistributed routes(for anyprotocol except IGRP or EIGRP) set metric metric

Set the metric value to give the redistributed routes(for IGRPor EIGRP only) set metric k1 k2 k3 k4 k5

Restore the metric to their default value no set metricSet the BGP origin code set origin { igp | egp as-number | incomplete }Remove the BGP origin code no set originSet the tag value to associate with the redistributed routes set tag tag-valueDelete the tag value to associate with the redistributed routes no set tag

By default, AS number, BGP community attribute, next hop, local preference, metricvalue, origin attribute and routing information tag field are not set.

8.2.5 Configure Route Redistribution

Routing protocols can share the routing information of others by redistribution. Whenthe routing information of other protocols are redistributed, the undesired routinginformation can be filtered by redistributing a route-map. The metric of distributeddestination routing protocol cannot exchange with that of the redistributed originalrouting protocol. At this time, a route metric should be specified for the redistributedroute.

Perform the following task in protocol configuration mode.

Table RC-8-4 Configure Route Redistribution

Operation Command

Configure route redistribution redistribute protocol [ metric metric ] [ tag tag-value ] [ type 1 | 2 ] [ route-map map-name ]

Cancel route redistribution no redistribute protocol

By default, a protocol does not redistribute routes from other domain into the its routingtable.

protocol specifies the source routing domain that can be redistributed. At present, it canredistribute routes domain such as connected, static, rip, igrp, eigrp, ospf, ospf-ase andbgp. And eigrp can redistribute the routes found by eigrp of other AS areas.

At present, software supports to redistribute routes information found by followingprotocols into the route table:



8-6

l connected: network segment (or host) route directly connected to the router’s

interface

l static: static route

l rip: routes discovered by rip

l igrp: routes discovered by igrpl eigrp: routes discovered by eigrp

l ospf: routes discovered by ospf

l ospf-ase: external routes discovered by ospf

l bgp: routes discovered by bgp

Note that an AS-number should be specified when redistributing the eigrp routes.

metric metric (optional) specifies the metric value of the redistributed routes. WhenIGRP and EIGRP routes are redistributed, the parameters k1 k2 k3 k4 k5 should alsobe specified. That is, metric bandwidth delay reliability loading mtu

bandwidth is the route bandwidth, ranging from 1 to 4294967295 kbytes/s.

delay is the route time delay, each unit stands for 10µs, ranging from 1 to 16777215

reliability is the channel reliability, ranging 0 to 255. 255 stands for 100% creditable.

loading is the channel seizure rate, ranging 1 to 255, 255 stands for 100% seized.

mtu is the largest transfer unit of route, ranging from 1 to 65535 byte.

route-map map-name (optional) specifies redistributed routes which matches thespecified route-map name. This item can be used in the routing protocol configurationexcept in the ospf protocol configuration mode.

tag tag-value (optional) sets the tag value of the redistributed route when ospf isredistributing other protocol routes.

type (optional) is the type of ospf external route corresponding to the redistributedroute when ospf is redistributing other protocol routes. type 1 refers to external routetype 1 and type 2 refers to external route type 2.

The metric value of the redistributed route can be set as the following:

1) Specify the metric value with set metric command.

2) Filter the route with route-map and set attributes for the route matching theconditions.

3) If neither of the above is specified, the redistributed route will use the default

metric value. The default metric can be specified with default-metric command.

When both route-map and metric value are specified, the routing information matchingthe route-map will use the metric specified by the set command of a route-map.

8.2.6 Define a Prefix-List Entry

A prefix-list is identified with the list name and consists of several parts, withsequence-number specifying the matching order of these parts. In each part, you canspecify an individual matching range in the form of network prefix.




8-7

In the process of matching, different parts of different sequence-numbers are of “OR”relation. That is to say, the routing information matches different parts in turn. Passing aspecific part of prefix-list is passing the filtering of this prefix-list.




8-8

Table RC-8-5 Define a Prefix-list Entry

Operation Command

Define a prefix-list entry ip prefix-list prefix-list-name [ seq seq-number ] { permit | deny } network/len[ ge ge-value ] [ le le-value ]

Cancel a prefix-list entry no ip prefix-list prefix-list-name [ seq seq-number ] [ permit | deny ]

By default, no prefix-list entry is defined.

8.2.7 Configure Route Filter

In some cases, only the routing information that meets the condition should bedistributed or redistributed, to prevent the neighbouring routers from knowing someroutes. Then the prefix-list or access-list in the route strategy can be quoted to filter therouting information.

Perform the following task in routing protocol configuration mode.

I. Configure Filtering Route Information Received

Define a strategic rule and quote an ACL or prefix-list to filter the routing informationthat does not meet the requirements when receiving routes. Specify a prefix-listthrough gateway keywords, filtering the address of the information router to receiveonly the updating messages from specific neighbouring routers.

Table RC-8-6 Configure Filtering Route Information Received

Operation Command

Filter the route information received from a specifiedgateway distribute-list gateway prefix-list-name in

Change or cancel filtering the route information receivedfrom a specified gateway no distribute-list gateway prefix-list-name in

Filter the route information received distribute-list {access-list-number | prefix-listprefix-list-name } in

Change or cancel filtering route information received no distribute-list {access-list-number | prefix-listprefix-list-name } in

II. Configure Filtering the Route Information being Advertised

Define a strategic rule and quote an ACL or prefix-list to filter the routing informationthat does not meet the requirements when receiving routes. Specify the protocol tofilter only the distributed protocol routing information.



8-9

Table RC-8-7 Configure Filtering Route Information being Advertised

Operation Command

Filter the route information being advertised distribute-list {access-list-number | prefix-list prefix-list-name } out [ protocol ]

Change or cancel filtering route informationbeing advertised

no distribute-list { access-list-number | prefix-list prefix-list-name } out [ protocol ]

By default, no route information received or being advertised is filtered.

protocol specifies the routing domain that can will be filtered. At present, eigrp can filterroutes domain as follows:

l connected: the network segment (host) route directly connected with the local

interface.

l static static routel rip route discovered by RIP protocol

l igrp route discovered by IGRP protocol

l eigrp route discovered by EIGRP protocol

l ospf route discovered by OSPF protocol

l ospf-ase external route discovered by OSPF protocoll bgp route discovered by BGP protocol

When the protocol is eigrp, the corresponding AS-number should also be specified.

8.3 Monitoring and Maintenance of IP Routing Protocol-Independent Features

Perform the following task in privileged user mode.

Table RC-8-8 Monitoring and maintenance of IP Routing Protocol-Independent Features

Operation Command

Show route-map show route-map [ map-name ]Show information of access-list show access-list [ access-list-number | all | interface type number ]Show prefix-list information show ip prefix-list [ prefix-list-name ]

1) Show the specified route-map

Quidway(config)# show route-map

Routemap : map1

permit 10 : match ip address(access-list) 1

set metric 100

matched : 0 denied : 0

permit 20 : match ip address (prefixlist) prefix1

set origin IGP

matched : 0 denied : 0

2) Show all information of access-list



8-10

Quidway(config)# show access-list

Using normal packet-filtering access rules now.

1 permit 20.1.1.0 0.0.0.3 (no matches -- rule 1)

1 permit 10.0.0.0 0.255.255.255 (no matches -- rule 2)

1 deny any (no matches -- rule 3)

3) Show all prefix-list information

Quidway(config)# show ip prefix-list

Prefix-list prefix1

seq 10: permit 43.0.0.0/8

8.4 Typical Configuration of IP Routing Protocol-IndependentFeatures

8.4.1 Configure Filtering Route Information Received


This example describes how IGRP protocol selectively redistributes RIP route. Thenetworking diagram is as follows.

The router connects a campus network and a regional local network. The campusnetwork uses RIP as the internal routing protocol and the local network uses IGRProuting protocol. Some routing information of the campus network should be distributedin the local network. To fulfil this function, IGRP protocol on the router filters the routesby quoting a route-map when redistributing RIP protocol routing information. Theroute-map consists of two nodes so that the routing information from 192.1.0.0/24 and128.2.0.0/16 are distributed by IGRP with different metric values.


Campus networkRouter

Local network

128.1.0.0

Figure RC-8-1 Networking diagram of configuring filtering received routes


! Configure prefix-list

Quidway(config)# ip prefix-list p1 permit192.1.1.0/24

Quidway(config)# ip prefix-list p2 permit 128.2.0.0/16

! Configure route-map



8-11

Quidway(config)# route-map r1 permit 10

Quidway(config-route-map)# match ip address prefix-list p1

Quidway(config-route-map)# set metric 10000 100 255 1 1500

Quidway(config)# route-map r1 permit 20

Quidway(config-route-map)# match ip address prefix-list p2

Quidway(config-route-map)# set metric 5000 200 255 1 1500

! Configure IGRP protocol

Quidway(config)# router igrp

Quidway(config-router-igrp)# network 128.1.0.0

Quidway(config-router-igrp)# redistribute rip route-map r1

8.4.2 Configure Filtering Route Information for OSPF


l Router A is in communication of Router B, and the link layer encapsulates PPP

protocol.

l Router A receives three static routes and the next hop is Ethernet interface.l Router B is configured with filtering rules, making the three static routes partially

visible and partially shielded. The routes of network segments 20.0.0.0 and

40.0.0.0 are visible and those of network segment 30.0.0.0 are filtered.


area 0

S0S0

static 20.0.0.1 30.0.0.1 40.0.0.1

Router A Router B

Figure RC-8-2 Networking diagram of configuring OSPF route filtering



! Configure IP address of Serial0, encapsulated to PPP protocol.



RouterA(config-if-Serial0)# encapsulation ppp

! Configure three static routes:

RouterA(config)# ip route 20.0.0.1 32 ethernet 0




8-12


! Start OSPF protocol and specify id of area including the interface.



RouterA(config-if-Seria0)# ip ospf enable area 0

! Redistribute static route

RouterA(config-router-ospf)# redistribute ospfase static




RouterB(config-if-Serial0)# encapsulation ppp

! Configure an access-list entry:

RouterB(config)# access-list 1 deny 30.0.0.0 0.255.255.255

RouterB(config)# access-list 1 permit any

! Start OSPF protocol and configure the area number of this interface



RouterB(config-if-Seria0)# ip ospf enable area 0

! Configure filtering route information received for OSPF

RouterB(config-router-ospf)# distribute-list 1 in

8.4.3 Configure Filtering Route Information


This example describes how RIP protocol publishes the routing information selectively.The router connects campus network A and campus network B, both of which use RIPas the internal routing protocol. The router needs to distribute the routes 192.1.1.0/24and 192.1.2.0/24 of campus A in the local network. To achieve this function, RIPprotocol on the router defines a distribute-list to filter the routing information, performthe route filtering function through quoting a prefix-list.


Campus network ARouter

202.1.1.0Campus network B

192.1.10.0

Figure RC-8-3 Networking diagram of filtering the distributed routing information



8-13


! Configure prefix-list

Router(config)# ip prefix-list p1 permit 192.1.1.0/24

! Configure RIP protocol

Router(config)# router rip

Router(config-router-igrp)# network 192.1.0.0

Router(config-router-igrp)# network 202.1.1.0

Router(config-router-igrp)# distribute-list prefix-list p1 out

8.5 Troubleshooting of IP Routing Protocol-Independent Features

Fault 1: Routing information can not be filtered when the routing protocol is in normaloperation

Troubleshooting: check the following to see if there is any error:

l At least one node in the route-map should be in permit matching mode. When a

route-map is used to filter routing information or a specific routing information does

not pass the filtering of a node, the routing information is considered not passing

the filtering of this route-map. When all nodes of the route-map are in deny mode,no routing information will pass the filtering of this route-map.

l At least one item in the prefix-list should be in permit matching mode. The list item

in deny mode can be defined to fast filtering routing information that does not meet

the conditions. But if all list items are in deny mode, no route will pass the filtering

of this prefix-list. Define a permit 0.0.0.0/0 list item after multiple items are definedin deny modes, so that all other routes will pass the filtering.

Fault 2: When an ACL is quoted for filtering routing information and ACL definition ismodified, the route strategy is not updated accordingly.

Troubleshooting: in this case, reconfigure quoting the strategy and rule of this ACL toinform the protocol of ACL change. If other filters are quoted, this operation is notnecessary and the protocols will be informed of the change of the router.

User Manual - Configuration Guide (Volume 2Versatile Routing Platform

Chapter 9 Configuration of IP Policy Routing

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9.1 Brief Introduction of IP Policy Routing

IP policy routing is a mechanism in which messages are transmitted and forwarded bystrategy without going through the routing table. It is a more flexible routing mechanism,compared with routing according to the destination address of data message. When arouter is forwarding a packet, it is filtered via a route map first, which will decide thepackets to be forwarded and the next router.

Policy routing is configured by the user. It is composed of a group of match clauses anda group of set clauses. When the messages of the policy routings are required to fullysatisfy the match clauses of strategy, set clauses in the strategy are executed in acertain sequence, to affect the message forwarding.

At present, two match clauses i.e. match length and match ip address are provided.

set clause defines the operation of the strategy. At present, there are five set clauses:set ip precedence , set interface, set ip next-hop, set default interface, set ipdefault next-hop. They are executed in sequence until the execution can no proceed.

There are two kinds of policy routings: interface policy routing and local policy routing.The former is configured in interface configuration mode and performs strategic routingfor messages from this interface, while the latter is configured in global configurationmode and performs policy routing for messages generated by this host. Generally, thelocal policy routing should not be configured.

The policy routing can be used for security and load sharing.

9.2 Configuring IP Policy Routing

9.2.1 IP Policy Routing Configuration Task List

IP policy routing configuration tasks are listed as follows:

l Create a Route-map

l Define match clause of policy routing

l Define set clause of policy routingl Enable/disable interface strategic route

9.2.2 Create a Route-map

The strategy specified with the strategy name may have several strategy points andeach strategy point are specified with sequence-num. The smaller the sequence-num,the higher the preference. And the defined strategy will be executed first. This strategycan be used to redistribute route and perform policy routing when IP messages areforwarded. When route-map is recreated, the configuration information of the new



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route-map will overwrite that of the old route-map. The contents of the strategy will bespecified by match and set clauses.

Please refer to “Configuration of IP Routing Strategy” for details.


Table RC-9-1 Create a Route-map

Operation Command

Create a route-map and enter into the Route-mapconfiguration mode route-map map-name { permit | deny} { seq-number }Delete a route-map no route-map map-name [ permit | deny ] [ seq-number ]

permit means policy routing for the messages meeting the conditions and deny meansno policy routing for the message meeting the conditions.

By default, no strategy is created.

9.2.3 Define Match Rules

IP policy routing provides two match clauses, i.e. matching strategy according to IPmessage length and IP address. One strategy includes multiple match clauses, whichcan be used in combination.


Table RC-9-2 Define match clauses

Operation Command

Specify matching condition for IP packet length match length min-len max-lenRemove matching condition for IP packet length no match lengthSpecify matching condition for IP address match ip address access-list-numberRemove matching condition for IP address no match ip address

By default, no match clause is defined.

9.2.4 Define Set Clause

IP policy routing provides 5 set clauses. One strategy includes multiple set clauses,which can be used in combination.


Table RC-9-3 Define set clause

Operation Command

Set message precedence set ip precedence valueCancel SET clauses setting message precedence no set ip precedenceSet message transmitting interface set interface type numberCancel SET clauses setting message transmittinginterface no set interface

Set message default transmitting interface set default interface type number



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Operation Command

Cancel SET clauses setting message default sendinginterface no set default interface

Set message next-hop set ip next-hop ip-addressCancel SET clauses setting message next-hop no set ip next-hopSet message default next-hop set ip default next-hop ip-addressCancel SET clauses setting message default next-hop no set ip default next-hop

The user can specify multiple next-hops or send the message to multiple interfaces.Generally, only the first parameter works. If the first parameter is mismatched, thesecond parameter will take effect, and so on and so forth.

By default, no set clause is defined.

9.2.5 Enabling/Disabling Local Policy Routing


Table RC-9-4 Enabling/disabling local policy routing

Operation Command

Enable local policy routing on the interface ip local policy route-map map-tagDisable local policy routing on the interface no ip local policy route-map map-tag

By default, local policy routing is disabled. Only one local policy route can beconfigured.

9.2.6 Enable/Disable Policy Routing on the Interface


Table RC-9-5 Enable/disable interface policy routing

Operation Command

Enable policy routing on the interface ip policy route-map map-tagDisable policy routing on the interface no ip policy route-map map-tag

By default, no policy routing is disabled on the interface.

9.3 Monitoring and Maintenance of IP Policy Routing

Perform the following task in the privileged mode.

Table RC-9-6 Monitoring and maintenance of IP policy routing

Operation Command

Turn on the debugging information switch of policy routing debug ip policy-routing



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9.4 Typical Configuration of IP Policy Routing

9.4.1 Configure Policy Routing Based on Source Address

I. Configuration requirement

Define a policy named “aaa” that includes two nodes, through which all TCP messagesare transferred from serial port 0 and the others are transferred from serial port 0.

l Node 10 indicates that messages matched with access-list 102 will be send toserial port 0.

l Node 20 indicates that all the other messages will be send to serial port 1.

The messages from Ethernet 0 will try to match MATCH clauses of nodes 10 and 20 inturn. If nodes in permit mode are matched, execute corresponding SET clauses. Ifnodes in deny mode are matched, exit from policy routing.

LAN A is connected with the Internet through Quidway series routers, requiring thatTCP messages are transmitted through path 1 and other messages are transmittedthrough path 2.


LAN A 10.110.0.0/255.255.0.0

Internert

QuidwayPath 1 Path 2

S0 S1

E0

Figure RC-9-1 Networking diagram of configuring policy routing based on source address


! Define access-list entry:

Quidway(config)# access-list 101 deny tcp 0.0.0.0 255.255.255.255 0.0.0.00.0.255.255

Quidway(config)# access-list 102 permit tcp 0.0.0.0 255.255.255.255 0.0.0.0255.255.255.255

! Define a node 10, indicating messages matching access-list 102 will be sent to serialport 1



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Quidway(config)# route-map aaa permit 10

Quidway(config-route-map)# match ip address 102

Quidway(config-route-map)# set interface serial 1

! Define node 20, indicating all the other messages will be sent to serial port 0

Quidway(config)# route-map aaa permit 20



! Adopting policy aaa in ethernet interface


Quidway(config-if-Ethernet0)# ip policy route-map aaa

9.4.2 Configuring Policy Routing Based on Message Size

I. Configuration requirement

Router A sends the messages of 64-100 bytes through S0, messages of 101-1000bytes through S1 and those of other size should be routed normally.

Apply IP policy routing lab1 on E0 of Router A. This strategy will set message of 64-100bytes to 150.1.1.2 as the IP address of next forwarding and set message of 101-1000bytes to 151.1.1.2 as the IP address of next forwarding. All messages of other levelsshould be routed in the method based on the destination address


Router A Router B

S0150.1.1.1

S0150.1.1.2

S1151.1.1.1

S1151.1.1.2

Apply strategy on E0 E0192.1.1.1

64-100 bytes

101-1000 bytes

Figure RC-9-2 Networking diagram of configuring policy routing based on message size





RouterA(config-if-Ethernet0)# ip policy route-map lab1




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RouterA(config)#router rip




RouterA(config)# route-map lab1 permit 10

RouterA(config-route-map)# match length 64 100

RouterA(config-route-map)# set ip next-hop 150.1.1.2

RouterA(config)# route-map lab1 permit 20

RouterA(config-route-map)# match length 101 1000

RouterA(config-route-map)# set ip next-hop 151.1.1.2






RouterB(config)# router rip



Monitor policy routing with debug ip policy command on Router A. Note: the messagesof 64 bytes match the entry item whose serial number 10 as shown in the routingdiagram lab1, therefore they are forwarded to 150.1.1.2.

RouterA# debug ip policy

IP: s=151.1.1.1(local),d=152.1.1.1, len 64, policy match

IP: route map lab1, item 10, permit

IP: s=151.1.1.1(local),d=152.1.1.1, len 64, policy routed

IP: local to serial 150.1.1.2

On Router A, change the message size to 101 bytes and monitor policy routing withdebug ip policy command. Note: the messages of 101 bytes match the entry itemwhose serial number 20 as shown in the routing diagram lab1. They are sent to151.1.1.2.


IP: s=151.1.1.1(local),d=152.1.1.1, len 101, policy match

IP: route map lab1, item 20, permit

IP: s=151.1.1.1(local),d=152.1.1.1, len 101, 64, policy routed

IP: local to serial 151.1.1.2



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On Router A, change the message size to 1001 bytes and monitor policy routing withdebug ip policy command. Note that this message does not match any entry item inlab1, so it is forwarded in regular mode.


IP:s=151.1.1.1(local),d=152.1.1.1, len 1001, policy rejected-normal

forwarding

IP:s=151.1.1.1(local),d=152.1.1.1, len 1001, policy rejected-normal

forwarding

Documents

05RC(Routing Protocol Configuration Guide)