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OBJECTIVES Upon completion of this chapter, you
should be able to:Read a routing tableConfigure a static routeCompare & contrast distance vector and
link state routing protocolsDescribe & configure RIPv1 & v2Describe & configure EIGRPDescribe & configure OSPF
BASICS Routers can be used to break network
smallerSubnet
To go from router to routerRouting tableFinds route to other networksStatically setDynamically learned
THE ROUTING TABLE Router looks at destination IP & SM
ANDing the destination IP & SM Result is a network # Looks in table for the match & forwards it out
that interface No match= default route, if set
Routing Table has list of networks & paths
STATIC ROUTE You telling the router:
“To get to this network, go this way!”
Used so routers do less “thinking” or when there’s only one way out of a networkStub networks or small networks
Same as default route config, but replacing quad zero with destination network address
CONFIGURING THE STATIC ROUTE
ip route destination_network subnet mask next hop ip or outgoing int
R1(config) #ip route 192.168.16.0 255.255.255.0 192.168.15.1
What would be the static route on R2 to reach the ladies’ network?
ACTIVITY Handout: Create static routes
Complete the PT lab togetherConfigure default and static routes
DYNAMIC ROUTING PROTOCOLS
Maintain tables when changes occurBad cables, interfaces go down, better route
learnedBest route to a network in tableRemoves routes when no longer valid
When all routers agree on topology= converged
Two routers can exchange these tables as long as they use the same protocol
DISTANCE VECTOR ROUTING
Passes updates every so often to connected neighbors
Distance & DirectionMetric (hops, speed, reliability, etc)
DISTANCE VECTOR ROUTING UPDATE METRIC
Directly connected network has an administrative distance of 0
Neighbors update each other & add on how far away it is
Star is 0 away
Star is 1 away
Star is 2 away
Star is 2 away
ACTIVITY 6.1.2.4
Activity for Routing TableDo together on SmartBoard
Create a Diagram from Routing TablesOn paper In groups of 2, create a topology based on
Routing Table
RIP
DV Metric is Hops
Only15 Max; 16 is unreachable (D) Updates every 30 seconds by default
Sends entire routing table (D) If change, update sent immediately (triggered)Slow to converge whole network (D)
Administrative Distance is 120
RIP RIPv1
Doesn’t send subnet mask in updatesClassful subnetting
RIPv2Classless (VLSM) subnettingSupports authenticationOtherwise, same as v1
CONFIGURE RIP Router(config)#router rip Router (config-router)#version 2 Router(config-router)#network network-number
DISADVANTAGES OF RIP
Increased traffic every 30 seconds
Max hop count of 15Further away is unreachable
Only considers hops, not speed
Possible routing loops
ACTIVITIES Configure RIP
In groups of 2, using the handout
PT Lab Configure & Verify RIP
Use our in class PT lab to configure RIP & verify it.
RIP Homework
REVIEW- 5Q What routing protocol uses hops for its
metric and understands classless routing? RIPv2
What is the AD of RIP? 120
What’s the purpose of entering your router’s network numbers when configuring RIP? To tell it what networks to advertise in updates
A directly connected network has an AD of… 0
A static route has an AD of… 1
EIGRP Enhanced Interior Gateway Routing
Protocol Cisco proprietary DV (mix LS & DV)AD of 90Many metrics (bandwidth, delay, load,
reliability)Up to 255 hopsRouting Table, Neighbor Table, Topology TableUpdates on start of router & only when a
change happensVLSM Support
CONFIGURE EIGRP R1(config)#router eigrp 100 R1(config-router)#network
192.168.1.193
Autonomous System #Must be the same on all routers in the
network
EIGRP TABLES Neighbor Table
Has info about neighbor direct connect routers Topology Table
Built from advertisements of its neighborsContains ALL routes advertised by neighbor
routersDUAL calculates the best path to a destination
and installs it into the routing table Is able to find the best alternate path quickly
when a network change occurs If no alternate route exists it asks its
neighbors to find a new path to the destination
REVIEW- 4Q How do you configure EIGRP?
Router eigrp as When viewing the routing table, what
letter indicates an EIGRP route?D
What 4 metrics are used for EIGRP?Bandwidth, load, delay, reliability
What algorithm calculates the best path for EIGRP?DUAL
LINK STATE ROUTING REVIEW
Knows all routes in your network Sends out LSA Makes a Topological database
With info from LSAs Uses the SPF algorithm
Each change causes new calc & database update
Map of network from point of view of the router
Info in tree is used to build the routing table Adds best path to routing table
WHAT IS OSPF? Most popular interior routing protocol
Multi-vendorUnlike Cisco’s EIGRP
Link-stateKnows map of whole networkRouting updates ONLY when change occurs
ALL ABOUT OSPF Uses SPF algorithm Sends updates only when the topology
changesDoes not send periodic updates of the
entire routing table AD of 110 Metric is cost (bandwidth) Fast convergence, no loops Supports VLSM/classless addressing Provides route authentication Multi-vendor (unlike EIGRP)
OSPF DATABASES Neighbor table
List of neighbor routersUnique to each router
Topology tableRepresents the whole networkAll routers have same one
Routing TableRoutes
THE ROUTER ID Tells neighbors who they are Is an IP address as follows:
Highest IP address on a loopback interface (virtual bc it never goes down)
No loopback= highest IP of active interfacesOr assigned manually
HELLO PACKETS Used to establish & maintain adjacency Helps elect Designated Router & BDR Sent every 10 seconds to 224.0.0.5
Dead after 40 seconds To form adjacency:
Hello, dead interval & area # must match
DR/BDR ELECTION One DR/BDR per multi-access area
(switch) All routers will form a full neighbor
adjacency with the DR Link updates sent to DR/BDR
Then forwards to other routersReduces LSA flood/traffic
Chosen by Priority #Highest is DR, next highest is BDRTie breaker is highest Router IDDefault on router is 1; 0 means NEVER!
OSPF AREAS OSPF works with the concepts of areas
Keeps the map of network smaller if you break it up into areas
By default you will always have a single areaNormally this is area 0
You can have multiple areasThey all connect to area 0 (the backbone)
See picture…
REVIEW- 4Q Area 0 is also known as what?
Backbone area If multiple areas are used, where must
they all connect to?Area 0
What do you know about link state protocols?Know whole topology, calculates shortest
path, updates when change happens To maintain connectivity to neighbors,
what do OSPF routers send?Hello packets
REVIEW- 4Q How often are hello packets sent?
Every 10 seconds What happens if you set the priority of
an interface to 0? It will NEVER be the DR/BDR
What is the metric for OSPF?Cost
What is the AD for OSPF?110
CONFIGURE THE ROUTERS
Interfaces Add a loopback
interface on each Int loopback 0 Ip address x.x.x.x
y.y.y.y
Student Center- 4.4.4.4 255.255.255.0
Science- 2.2.2.2 Admin- 1.1.1.1
OSPF COMMANDS ScienceBuilding(config)#router ospf 1 ScienceBuilding(config-
router)#network 192.168.23.0 0.0.0.255 area 0
AdminBuilding(config)#router ospf 1 AdminBuilding(config-router)#network
192.168.23.0 0.0.0.255 area 0
Process ID Wildcard mask
WILDCARD MASK Think of a wildcard mask as the inverse of a
subnet mask. The inverse of the subnet mask
255.255.255.252 is 0.0.0.3. To calculate the inverse of the subnet mask,
subtract the subnet mask from 255.255.255.255:
255.255.255.255 – 255.255.255.252 Subtract the sm
0. 0. 0. 3 Wildcard mask
VERIFY StudentCenter#show ip ospf
neighbor
AdminBuilding#show ip protocols
AdminBuilding#show ip route ospf
REVIEW-4Q If all OSPF routers in a single area have the
same priority, what value does a router use for the OSPF router ID in the absence of a loopback interface? Highest IP address of active interfaces
What will happen if the routers have different process-IDs? Nothing
What is the router ID used for? Election of the DR/BDR
What 2 things does OSPF use to build & maintain its databases? Hello packets & LSAa
SUMMARY OF ROUTING PROTOCOLS
Protocol DV or LS AD Metric Features
RIP v1 DV 120 Hops 15 hops max
RIP v2 DV 120 Hops15 max;VLSM
EIGRP DV-Hybrid 90
Bandwidth, Load, Delay, Reliability
Cisco’s;VLSM
OSPF LS 110 CostMulti-vendor;VLSM
REVIEW- 3Q You are configuring a new router. The
interfaces have been configured but no routing protocols or static routes. What routes would be in the routing table? Directly connected ones
What would cause 2 routers to NOT form an adjacency? The hello, dead, or area #’s don’t match
A router learns of 3 routes to one destination; they are from RIP, EIGRP, and OSPF. Which one will be put in the routing table and why? The EIGRP one. It has the lowest AD.
REVIEW- 4Q After an OSPF network has converged,
what messaging gets exchanged between routers?Hello packets
What is the default AD of OSPF?110
What is the default priority # for Cisco routers in the DR election process?1
What priority # would you set on a router if you did NOT want it to be a DR/BDR?0
REVIEW- 4Q An OSPF router will use a Router ID
based on what?Highest IP of loopback or highest IP of
active int. C 192.168.12.253/30 [110/782] via
192.168.12.233, 00:35:37, Serial 0What does the 782 mean?Cost
What address do hello packets get sent to?224.0.0.5
What does OSPF use to calculate cost?Bandwidth