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Instructor & Todd Lammle. Sybex CCNA 640-802 Chapter 7: EIGRP and OSPF. Chapter 7 Objectives. Enhanced IGRP EIGRP tables Configuring EIGRP Verifying EIGRP Open Shortest Path First Configuring OSPF Verifying OSPF Configuring OSPF with wildcards. 2. Enhanced IGRP supports:

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instructor todd lammle
Instructor & Todd Lammle

Sybex CCNA 640-802

Chapter 7: EIGRP and OSPF

chapter 7 objectives
Chapter 7 Objectives
  • Enhanced IGRP
    • EIGRP tables
    • Configuring EIGRP
    • Verifying EIGRP
  • Open Shortest Path First
    • Configuring OSPF
    • Verifying OSPF
    • Configuring OSPF with wildcards


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)

What Is Enhanced IGRP (EIGRP)?

IP RoutingProtocols

IP RoutingProtocols

AppleTalk Routing Protocol


AppleTalk Routing Protocol

IPX RoutingProtocols

IPX RoutingProtocols

comparing eigrp and igrp
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

Enhanced IGRP



  • No updates. Route updates sent only when a change occurs – multicast on
  • Hello messages sent to neighbors every 5 seconds (60 seconds in most WANs)


eigrp terminology

Topology Table—IP

Destination 1 Successor

Destination 1 Feasible Successor

Routing Table—IP

Destination 1 Successor

EIGRP Terminology

Neighbor Table—IP

Next Hop Interface Router

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

eigrp tables

Enhanced IGRP



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


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

successor routes

Topology Table—IP

Destination 1 Successor

Destination 1 Feasible Successor

Routing Table—IP

Destination 1 Successor

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
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)

Choosing Routes















configuring eigrp for ip
Configuring EIGRP for IP





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

Enable EIGRP

Assign networks

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


Redistribution is translating one type of routing protocol into another.



Router B

Router D

Router A

Router C

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

route path
Route Path

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







verifying enhanced igrp operation
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

Verifying Enhanced IGRP Operation

show ip eigrp neighbors


show ip eigrp topology


show ip route eigrp


show ip protocols


show ip eigrp traffic


show ip route
Show IP Route

P1R1#sh ip route

[output cut]

Gateway of last resort is not set

D [90/2172] via,00:04:36, Serial0/0

C is directly connected, FastEthernet0/0

D [90/2681] via,00:04:36, Serial0/0

C is directly connected, Serial0/0

D [90/2707] via,00:04:35, Serial0/0


-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


Introducing OSPF

  • Open standard
  • Shortest path first (SPF) algorithm
  • Link-state routing protocol (vs. distance vector)
  • Can be used to route between AS’s
ospf hierarchical routing
Consists of areas and autonomous systems

Minimizes routing update traffic

Supports VLSM

Unlimited hop count

OSPF Hierarchical Routing
link state vs distance vector
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
Types of OSPF Routers

Area 1

Backbone Area 0

Area 2

ABR and BackboneRouter




ASBR andBackbone Router

ABR and BackboneRouter

  • External AS
configuring single area ospf
Configuring Single Area OSPF

Router(config)#router ospf process-id

Defines OSPF as the IP routing protocol

Note: The process ID is locally significant and is needed

to identify a unique instance of an OSPF database

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

Assigns networks to a specific OSPF area

ospf example


Area 0



OSPF Example
verifying the ospf configuration
Verifying the OSPF Configuration

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 interface

Displays area-ID and adjacency information

Router#show ip ospf neighbor

Displays OSPF-neighbor information on a per-interface basis

osfp neighbors
OSFP Neighbors
  • OSPF uses hello packets to create adjacencies and maintain connectivity with neighbor routers
  • OSPF uses the multicast address


  • 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
OSPF Terminology
  • Neighbor
  • Adjacency








router id rid
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

Electing the DR and BDR

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
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
Interface Priorities

What is the default OSPF interface priority?

Router# show ip ospf interface ethernet0/0

Ethernet0 is up, line protocol is up

Internet Address, Area 4

Process ID 19, Router ID, Network Type BROADCAST,

Cost: 10 Transmit Delay is 1 sec, State DR, Priority 1

Designated Router (ID), Interface address

No backup designated router on this network

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

Hello due in 00:00:06

Index 2/2, flood queue length 0

Next 0x0(0)/0x0(0)

Last flood scan length is 0, maximum is 0

Last flood scan time is 0 msec, maximum is 0 msec

Neighbor Count is 0, Adjacent neighbor count is 0

Suppress hello for 0 neighbor(s)

ensuring your dr
Ensuring your DR

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

configuring wildcards
Configuring Wildcards

If you want to advertise a partial octet (subnet), you need to use wildcards.

  • means all octets match exactly
  • means that the first three match exactly, but the last octet can be any value

After that, you must remember your block sizes….


The wildcard address is always one less than the block size….

  • =
  • =
  • =
  • =
wildcard configuration of the lab b router
Wildcard Configuration of the Lab_B Router
  • Lab_A
  • E0:
  • S0:
  • Lab_C
  • E0:
  • S1:
  • Lab_B
  • E0:
  • S0:
  • S1:
  • Go through all the written and review questions
  • Go over the answers with the class