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7/26/2019 Routing Protcols
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Report
Major Routing Protocols
Submitted by: Saeed Ali Shahani (Intern)
Submitted to:(Solution Provisioning Engineering) SPE South Team
Date: 10-5-2016
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Table of Contents
1 What is Routing Protocol?...........................................................................................................3
1.1 Types of Routing .................................................................................................................3
1.1.1 Static Routing ..............................................................................................................3
1.1.2 Dynamic Routing Protocols ..........................................................................................3
1.2 Classification .......................................................................................................................3
1.3 Types of Routing Protocols ..................................................................................................4
1.3.1 Distance Vector ...........................................................................................................4
1.3.2 Link State .....................................................................................................................4
2 RIP (Routing Information Protocol) .............................................................................................5
3 EIGRP (Enhanced Interior Gateway Routing Protocol) ..................................................................6
4 OSPF (Open Shortest Path First) ..................................................................................................7
4.1 Introduction ........................................................................................................................7
4.2 OSPF Packet Type ................................................................................................................8
1. Hello: ..................................................................................................................................8
2. DD/DBD: .............................................................................................................................8
3. LSR: ....................................................................................................................................8
4. LSU: ....................................................................................................................................8
5. LSAck: .................................................................................................................................8
4.3 Router ID ............................................................................................................................8
4.4 Key points ...........................................................................................................................8
4.5 OSPF Tables:- ......................................................................................................................9
4.6 OSPF 7-States diagram ........................................................................................................9
4.7 LSA Types .......................................................................................................................... 10
4.8 Router and Area Types ...................................................................................................... 11
5 BGP (Border Gateway Protocol) ................................................................................................ 12
5.1 Introduction ...................................................................................................................... 12
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1 What is Routing Protocol?
The process of moving a packet of data from source to destination. Routingis usually performed by a
dedicated device called a router.
A routing protocol specifies how routers communicate with each other
A routing algorithm determine the specific choice of route
1.1 Types of Routing
1.
Static
2.
Dynamic
1.1.1 Static Routing
Hand type all network locations in routing table
Ideal for Small Organization Simplest form of Routing
One way communication
Static routes use less bandwidth than dynamic routes
No CPU cycles are used to calculate and analyze routing updates.
1.1.2 Dynamic Routing Protocols
Place information in routing table. If change occur it update the routing table automatically with all the
information
1.2 Classification
1. IGPstands Internal Gateway Protocol :work as a single autonomous number within small
organization
2.
EGPStands External Gateway Protocol :used for internet ISPs
IGP EGP RIP BGP (Border Gateway Protocol)
OSPF - EBGP (Exterior Border Gateway Protocol)
IGRP - IBGP (Interior Border Gateway Protocol)
EIGRP (Cisco Proprietary)
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1.3 Types of Routing Protocols
1.3.1 Distance Vector
It only look distance
Take shortest-path
Used in RIP,IGRP
1.3.2 Link State
Used in OSPF
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2 RIP Routing Information Protocol)
Routing Information Protocol (RIP) is a distance-vector routing protocol. RIP sends the complete routing
table out to all active interfaces every 30 seconds. RIP only uses hop count (the number of routers) to
determine the best way to a remote network.
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3 EIGRP Enhanced Interior Gateway Routing Protocol)
EIGRP is an enhanced version of IGRP. The same distance vector technology found in IGRP is also used in
EIGRP, It is a Cisco proprietary protocol.
It doesnt send link state packet like OSPF, but it send distance-vector plus reaching cost from
perspective of router
Best Path Selection with DUAL (Diffusing Update Algorithm)
Fast convergence
Efficient in neighbor discovery
Maximum Hop count 255
Load balancing over unequal cost links
Classless (VLSM support)
Hybrid routing protocol (distance vector that has link-state characteristics)
Multicast - 224.0.0.10
IP protocol 88
Neighbors advertise distance to specific network(s)
Default composite metric of bandwidth and delay
Load, reliability and MTU can be factored into metric
Send specific updates only when topology change occur
Admin distance is
-
90 for EIGRP internal routes
-
170 for EIGRP external routes
-
5 for EIGRP summary routes.
-
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4 OSPF Open Shortest Path First)
4.1 Introduction
Open-Shortest-Path-First (OSPF) is the most widely used interior gateway protocol routing protocol on
the world because it is a public (non-proprietary) routing protocol while its biggest rival, EIGRP, is a Cisco
proprietary protocol so other vendors cant use it. OSPF is a complex link -state routing protocol. Linkstate routing protocols generate routing updates only when a change occurs in the network topology.
When a link changes state, the device that detected the change creates a link-state advertisement (LSA)
concerning that link and sends to all neighboring devices using a special multicast address. Each routing
device takes a copy of the LSA, updates its link-state database (LSDB), and forwards the LSA to all
neighboring devices.
OSPF routers use LSA (Link State Advertisement) to describe its link state. LSDB stores all LSAs.
A router uses Router LSA to describe its interface IP addresses.
After OSPF is started on a router, it creates LSDB that contains one entry: this routers Router
LSA.
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4.2 OSPF Packet Type
5-type - 10/40 sec, 30/120 sec
1.
Hello:are used to establish and maintain adjacency with other OSPF routers
2. DD/DBD: The neighboring router with the highest priority is elected as the DR
3.
LSR:
used by receiving routers to request more information about any entry in the DBD
4. LSU:
used to reply to LSRs as well as to announce new information.
5.
LSAck:sent to confirm receipt of an LSU message
4.3 Router ID
The router is known to OSPF by the OSPF route id
By default the router id is the highest IP address on an active interface
A loopback interface can override the OSPF router id
The OSPF router id command can be used to override the OSPF router id
Using the loopback interface or router id command is recommended for stability
4.4 Key points
Is a public (non-proprietary) routing protocol. Is the only link-state routing protocol.
This works by using the Dijkstra algorithm
Information about its neighbors (local connectivity) is sent to the entire network using
multicasting
The entire routing table is transmitted once every 30 minutes
Routing information is shared through Link-state updates (LSAs)
HELLO messages are used to maintain adjacent neighbors
Is a classless routing protocol because it does not assume the default subnet masks are used. It
sends the subnet mask in the routing update. + Supports VLSM and route summarization
Uses COST as a metric which CISCO defines as the inverse of the bandwidth
Uses AREAs to subdivide large networks, providing a hierarchical structure and limit the
multicast LSAs within routers of the same area
Area 0 is called backbone areaand all other areas connect directly to it. All OSPF networks
must have a backbone area
Area Border Routers (ABR) are any routers that have one interface in one area and another
interface in another area
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4.5 OSPF Tables:-
Neighbor Table: - Adjacency Database, List of recognized neighbor
Topology Table: - Contain all routers & their attached links in the area; LSDB
Routing Table: - Best path to destination
4.6 OSPF 7-States diagram
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4.7 LSA Types
OSPF Virtual Link: - Once the ospf router becomes adjacencies then the virtual link will be up. If
between the routers there is firewall then we need to open port 89 first. Area cant be stub area.
At least one end reside at area 0
Both end router must share the common area
Route Summarization: - Route summarization can reduce the number of routes that a router
must maintain, because it is a method of representing a series of network in a single summary
address
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4.8 Router and Area Types
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5 BGP Border Gateway Protocol)
5.1 Introduction
Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange
routing and reachability information between autonomous systems (AS)on the Internet.
The protocol is often classified as a path vector protocolbut is sometimes also classed as a distance
vector routing protocol. The Border Gateway Protocol makes routing decisions based on paths, network
policies, or rule-setsconfigured by a network administrator and is involved in making core routing
decisions.
BGP may be used for routing within an autonomous system. In this application it is referred to as
Interior Border Gateway Protocol, Internal BGP, or iBGP. In contrast, the Internet application of the
protocol may be referred to as Exterior Border Gateway Protocol, External BGP, or EBGP.
Figure
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5.2 Multihoming Environment
Having two or more upstream providers for internet connectivity is considered as Multihoming
Environment. Multihoming ensures redundancy with best available path towards the specified
destination. BGP is considered as the best protocol to be used in this environment.
Following techniques are available to implement Multihoming
5.2.1 Stub Network
Two or more links to the same ISP
No need for BGP
Point static default to upstream ISP oUpstream ISP advertises stub network
Policy confined within upstream ISPs policy
5.2.2 Multihomed Stub Network
Two or more links to different ISPs Through a Single Local Router
Use BGP (not IGP or static) to load share
Use private AS (ASN > 64511) oUpstream ISP advertises stub network
Policy confined within upstream ISPs policy
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5.2.3 Multihomed Network
Two or more links to different ISPs Through Multiple Local Routers
Many scenarios are possible
-Multiple sessions to same ISP
-Secondary for backup only
-Load-share between primary and secondary
-Selectively use different ISPs
5.3 BGP over OSPF
The first reason is that BGP is more scalable than OSPF.
E.g. the ISP level of routing do had large number of routes, which igp routing protocols like ospf cannot
handle. BGP can handle such large routes between AS.
Second reason is that bgp allows more options for routing manipulations and optimization by using
routing policies (by manipulating attributes)which is required when routing between AS , and this,
normal igp like ospf cannot perform.
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