Sybex CCNA 640-802Chapter 7: EIGRP and OSPF

Instructor & Todd Lammle

Chapter 7 Objectives

• Enhanced IGRP– EIGRP tables– Configuring EIGRP– Verifying EIGRP

• Open Shortest Path First– Configuring OSPF– Verifying OSPF– Configuring OSPF with wildcards

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What Is Enhanced IGRP (EIGRP)?

• Enhanced IGRP supports:– Rapid convergence– Reduced bandwidth usage– Multiple network-layer support– Uses Diffused Update Algorithm (DUAL) to select loop-free

routes and enable fast convergence– Up to six unequal paths to a remote network (4 by default)

EnhancedIGRP

IPX RoutingProtocols

AppleTalk Routing Protocol

IP RoutingProtocols

IPX RoutingProtocols

AppleTalk Routing Protocol

IP RoutingProtocols

Comparing EIGRP and IGRP

– Similar metric– Same load balancing– Improved convergence time– Reduced network overhead– Maximum hop count of 255 (100

default)– EIGRP can differentiate

between internal and external routes

EIGRP for IP

• No updates. Route updates sent only when a change occurs – multicast on 224.0.0.10

• Hello messages sent to neighbors every 5 seconds (60 seconds in most WANs)

Enhanced IGRP

EIGRP EIGRP

hello

EIGRP Terminology

Neighbor Table—IPNext Hop Interface Router

Topology Table—IPDestination 1 SuccessorDestination 1 Feasible Successor

Routing Table—IPDestination 1 Successor

Note: A feasible successor is a backup route and stored in the Topology table

EIGRP Tables

• The neighbor table and topology table are held in ram and are maintained through the use of hello and update packets.

Enhanced IGRP

EIGRP EIGRP

hello

To see all feasible successor routes known to a router, use the show ip eigrp topology command

Successor routes

• Successor route is used by EIGRP to forward traffic to a destination

• A successor routes may be backed up by a feasible successor route

• Successor routes are stored in both the topology table and the routing table

Routing Table—IPDestination 1 Successor

Topology Table—IPDestination 1 SuccessorDestination 1 Feasible Successor

Choosing Routes

• EIGRP uses a composite metric to pick the best path: bandwidth and delay of the line

• EIGRP can load balance across six unequal cost paths to a remote network (4 by default)

IPX

19.2

T1

T1 T1

IPX

AppleTalk

IP

AppleTalk

IPA B

DC

Configuring EIGRP for IP

172.16.10.010.110.1.0192.168.0.0

TokenRing

AS=10

Router(config)#router eigrp 10Router(config-router)#network 10.0.0.0Router(config-router)#network 172.16.0.0

192.168.0.0

A C

B

Enable EIGRP

Assign networks

If you use the same AS number for EIGRP as IGRP, EIGRP will automatically redistribute IGRP into EIGRP

Redistribution

Redistribution is translating one type of routing protocol into another.

Router D

Router B

Router A

Router C

EIGRP IGRP

IGRP and EIGRP translate automatically, as long as they are both using the same AS number

Route Path

Assuming all default parameters, which route will RIP (v1 and v2) take, and which route will EIGRP take?

T1 T1

100BaseT

100BaseT

10BaseT

56K

Verifying Enhanced IGRP Operation

show ip protocolsRouter#

show ip route eigrp Router#

show ip eigrp traffic Router#

show ip eigrp neighbors Router#

show ip eigrp topology Router#

• Displays the neighbors discovered by IP Enhanced IGRP

• Displays the IP Enhanced IGRP topology table

• Displays current Enhanced IGRP entries in the routing table

• Displays the parameters and current state of the active routing protocol process

• Displays the number of IP Enhanced IGRP packets sent and received

Show IP Route

-D is for “Dual”

-[90/2172] is the administrative distance and cost of the route. The cost of the route is a composite metric comprised from the bandwidth and delay of the line

P1R1#sh ip route[output cut]Gateway of last resort is not setD 192.168.30.0/24 [90/2172] via 192.168.20.2,00:04:36, Serial0/0C 192.168.10.0/24 is directly connected, FastEthernet0/0D 192.168.40.0/24 [90/2681] via 192.168.20.2,00:04:36, Serial0/0C 192.168.20.0/24 is directly connected, Serial0/0D 192.168.50.0/24 [90/2707] via 192.168.20.2,00:04:35, Serial0/0P1R1#

•Open standard•Shortest path first (SPF) algorithm•Link-state routing protocol (vs. distance vector)•Can be used to route between AS’s

Introducing OSPF

OSPF Hierarchical Routing

• Consists of areas and autonomous systems• Minimizes routing update traffic• Supports VLSM• Unlimited hop count

Link State Vs. Distance Vector

Link State:• Provides common view of entire topology• Calculates shortest path• Utilizes event-triggered updates• Can be used to route between AS’s

Distance Vector:•Exchanges routing tables with neighbors•Utilizes frequent periodic updates

Types of OSPF Routers

InternalRouters

Area 1 Area 2

ASBR andBackbone Router

Backbone/InternalRouters

ABR and BackboneRouter

Backbone Area 0

ABR and BackboneRouter

InternalRouters

•External AS

Router(config-router)#network address mask area area-id

Assigns networks to a specific OSPF area

Router(config)#router ospf process-id

Defines OSPF as the IP routing protocolNote: The process ID is locally significant and is needed to identify a unique instance of an OSPF database

Configuring Single Area OSPF

OSPF Example

hostname R3

router ospf 10 network 10.1.2.3 0.0.0.0 area 0network 10.1.3.1 0.0.0.0 area 0

hostname R2

router ospf 20network 10.0.0.0 0.255.255.255 area 0

hostname R1

router ospf 30network 10.1.0.0 0.0.255.255 area 0network 10.5.5.1 0.0.0.0 area 0

R3

R2R1

10.1.2.0

10.1.1.0

10.5.5.0

Area 010.1.3.0

Router#show ip ospf interface

Verifying the OSPF Configuration

Displays area-ID and adjacency information

Router#show ip protocols

Verifies that OSPF is configured

Router#show ip route

Displays all the routes learned by the router

Router#show ip ospf neighbor

Displays OSPF-neighbor information on a per-interface basis

OSFP Neighbors• OSPF uses hello packets to create

adjacencies and maintain connectivity with neighbor routers

• OSPF uses the multicast address 224.0.0.5

Hello?224.0.0.5

•Hello packets provides dynamic neighbor discovery•Hello Packets maintains neighbor relationships•Hello packets and LSA’s from other routers help build and maintain the topological database

OSPF Terminology

• Neighbor

• Adjacency Neighbors

Cost=6

ABR

BDR

DR

Non-DRAdjacencies

Router ID (RID)

Each router in OSPF needs to be uniquely identified to properly arrange them in the Neighbor tables.

Electing the DR and BDR

• OSPF sends Hellos which elect DRs and BDRs

• Router form adjacencies with DRs and BDRs in a multi-access environment

Multicast Hellos are sent and compared

Router with Highest Priority is Elected as DR

Router with 2nd Highest Priority is Elected as BDR

Configuring Loopback Interfaces

Router ID (RID): – Number by which the router is known to OSPF– Default: The highest IP address on an active interface at the

moment of OSPF process startup– Can be overridden by a loopback interface: Highest IP address

of any active loopback interface – also called a logical interface

Interface Priorities

What is the default OSPF interface priority?Router# show ip ospf interface ethernet0/0Ethernet0 is up, line protocol is upInternet Address 192.168.1.137/29, Area 4Process ID 19, Router ID 192.168.1.137, Network Type BROADCAST,Cost: 10 Transmit Delay is 1 sec, State DR, Priority 1Designated Router (ID) 192.168.1.137, Interface address 192.168.1.137No backup designated router on this networkTimer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5Hello due in 00:00:06Index 2/2, flood queue length 0Next 0x0(0)/0x0(0)Last flood scan length is 0, maximum is 0Last flood scan time is 0 msec, maximum is 0 msecNeighbor Count is 0, Adjacent neighbor count is 0Suppress hello for 0 neighbor(s)

Ensuring your DR

What options can you configure that will ensure that R2 will be the DR of the LAN segment?

Configuring Wildcards

If you want to advertise a partial octet (subnet), you need to use wildcards.– 0.0.0.0 means all octets match exactly– 0.0.0.255 means that the first three

match exactly, but the last octet can be any value

After that, you must remember your block sizes….

Wildcard

The wildcard address is always one less than the block size….– 192.168.10.8/30 = 0.0.0.3– 192.168.10.48/28 = 0.0.0.15– 192.168.10.96/27 = 0.0.0.31– 192.168.10.128/26 = 0.0.0.63

Wildcard Configuration of the Lab_B Router

• Lab_A• E0: 192.168.30.1/24• S0: 172.16.10.5/30

• Lab_B• E0:

192.168.40.1/24• S0:

192.168.10.10/30• S1:

192.168.10.6/30

• Lab_C• E0:

192.168.50.1/24• S1:

172.16.10.9/30

Summary

• Go through all the written and review questions

• Go over the answers with the class

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