eigrp and ospf

8/3/2019 Eigrp and Ospf

http://slidepdf.com/reader/full/eigrp-and-ospf 1/30

AITA\SWBU\CCNA\08 1

EIGRP and OSPF



AITA\SWBU\CCNA\08 2

Objectives

• Enhanced IGRP

– EIGRP tables – Configuring EIGRP

– Verifying EIGRP

• Open Shortest Path First

– Configuring OSPF – Verifying OSPF

– Configuring OSPF with wildcards



AITA\SWBU\CCNA\08 3

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 andenable fast convergence

– Up to six unequal paths to a remote network (4 by default)

EnhancedIGRP

IPX RoutingProtocols

AppleTalkRouting Protocol

IP RoutingProtocols

IPX RoutingProtocols

AppleTalkRouting Protocol

IP RoutingProtocols



AITA\SWBU\CCNA\08 4

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 andexternal routes



AITA\SWBU\CCNA\08 5

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



AITA\SWBU\CCNA\08 6

EIGRP Terminology

Neighbor Table—IP

Next Hop Interface

Router

Topology Table—IPDestination 1 Successor

Destination 1 Feasible Successor

Routing Table—IP

Destination 1 Successor

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

the Topology table



AITA\SWBU\CCNA\08 7

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



AITA\SWBU\CCNA\08 8

Successor routes

• Successor route is used by EIGRP to forward traffic to adestination

• A successor routes may be backed up by a feasiblesuccessor 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



AITA\SWBU\CCNA\08 9

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 pathsto a remote network (4 by default)

IPX

19.2

T1

T1 T1

IPX

AppleTalk

IP

AppleTalk

IPA B

DC



AITA\SWBU\CCNA\08 10

Configuring EIGRP for IP

172.16.10.010.110.1.0192.168.0.0

Token

RingAS=10

Router(config)#router eigrp 10

Router(config-router)#network 10.0.0.0

Router(config-router)#network 172.16.0.0

192.168.0.0

A CB

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

Router# show ip protocols

Router# show ip route eigrp

Router# show ip eigrp traffic

Router# show ip eigrp neighbors

Router# show ip eigrp topology

• Displays the neighbors discovered by IPEnhanced IGRP

• Displays the IP Enhanced IGRP topologytable

• Displays current Enhanced IGRP entries inthe routing table

• Displays the parameters and current stateof the active routing protocol process

• Displays the number of IP Enhanced IGRPpackets 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, Serial0/0

C 192.168.10.0/24 is directly connected, FastEthernet0/0

D 192.168.40.0/24 [90/2681] via 192.168.20.2,00:04:36, Serial0/0

C 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, Serial0/0

P1R1#




• 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 andBackboneRouter

Backbone/InternalRouters

ABR andBackboneRouter

Backbone Area 0

ABR andBackboneRouter

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 protocol

Note: 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 20

network 10.0.0.0 0.255.255.255

area 0

hostname R1

router ospf 30

network 10.1.0.0 0.0.255.255area 0

network 10.5.5.1 0.0.0.0 area 0

R3

R2

R1

10.1.2.0 10.1.1.0

10.5.5.0

Area 0

10.1.3.0




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 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

Hello?

224.0.0.5




OSPF Terminology

• Neighbor • Adjacency

Neighbors

Cost=6

ABR

BDR

DR

Non-DR Adjacencies




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-accessenvironment

Multicast Hellos are sent and comparedRouter 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 anyactive loopback interface – also called a logical interface




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 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 1

Designated Router (ID) 192.168.1.137, Interface address 192.168.1.137

No backup designated router on this network

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

Hello due in 00:00:06Index 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 0Suppress hello for 0 neighbor(s)




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

eigrp and ospf

Documents