BSCI7 Redistribution PPT

1

Manipulating Manipulating Multiple Routing Multiple Routing

ProtocolsProtocols

(Redistribution)(Redistribution)July 2007July 2007

2Why we need multiple routing protocols?Why we need multiple routing protocols?A) Migration

-From FLSM to VLSM

-From flat design to hierarchical design (to facilitate route summarization which enhance network scalability)

3Why we need multiple routing protocols?Why we need multiple routing protocols?

B) Boundary between ASs

C) Different departments might require different routing needs

D) Unix host based routing (centre that contain UNIX servers) run RIP only, but your network require another protocol for inter routing

E) Mixed router vendor environment (use EIGRP on Cisco routers, use OSPF on non-Cisco router)

4RedistributionRedistribution• It is the mechanism that allow to connect different domains, so as the different Routing

protocol can exchange and advertise routing updates as if they are a single protocol

• The redistribution is performed on the router that lies at the boundary between different domains or runs multiple protocols

5Methods of redistributionMethods of redistribution• One way redistribution:

redistribute networks learned by a certain protocol in a single direction

• Two way redistribution:

redistributes all routes from a routing process to another and vice-versa

Redistributing VS. Redistributed protocolRedistributing VS. Redistributed protocol• Redistributing protocol:

It is the native protocol that will transform another protocol to its form

• Redistributed Protocol:

It is the non-native protocol that will be transformed to another protocol form

- note: in order for any routes to be redistributed it must exist in the routing table of the redistributing router

6Redistribution issuesRedistribution issues

1) Administrative Distance:

The redistributed protocol inherit the admin. distance of the redistributing protocol

2)Metric:

a seed metric (initial metric) is assigned to a redistributed route, then that metric is incremented according to the normal redistributing protocol policies

• The seed metric is adjusted from:

1-The default-metric command

2-The redistribution command using metric option or route map option (override the default-metric command)

7Default Seed metricsDefault Seed metrics• If Redistributing is

-RIPRIP metric is infinity

-IGRP/EIGRP IGRP/EIGRP metric is infinity

-OSPFOSPF metric is

20 (external type2) for all

except 1 (type2) for BGPBGP

& Subnets do not redistribute

by default

-IS-IS IS-IS metric is 0 (level2)

so RIP/IGRP/EIGRP does not advertise a redistributed route unless a seed metric is configured

8Redistribution Implementation Redistribution Implementation Consideration and problemsConsideration and problems

1-Two exit points with one way redistribution on both points on the same way

This will cause Routing loops 2-Two exit points with one way redistribution on both

points on the opposite ways

This will cause Routing feedback (incompatible routing information)

3-Two exit points with one way redistribution on only one of the points

This will cause sub-optimal path selection

4- Inconsistent convergence time:

Different routing protocols converge at different times

9Redistribution TechniquesRedistribution Techniques• We can conclude that existence of two exit point will cause a problem so we must use one of the

following:

1)Redistribute in a way and use default or static routes in the other way

2)Redistribute in both ways and use route filters (to filter any route trying to be redistributed back)

3)Redistribute in both ways and change admin. distance (make admin. distance of external routes higher than internal routes. EIGRP does that by default)

10Configuring RedistributionConfiguring Redistribution

• Redistribution supports all protocols

RIP, IGRP, EIGRP, OSPF, IS-IS, ISO-IGRP, ODR, BGP, Static and Connected

RtrA(config-router)# redistribute ?bgp Border Gateway Protocol (BGP)connected Connectedegp Exterior Gateway Protocol (EGP)eigrp Enhanced Interior Gateway Routing Protocol (EIGRP)igrp Interior Gateway Routing Protocol (IGRP)isis ISO IS-ISiso-igrp IGRP for OSI networksmobile Mobile routesodr On Demand stub Routesospf Open Shortest Path First (OSPF)rip Routing Information Protocol (RIP)static Static routes

11• But consider the following:

1-Redistribution vary slightly among different protocols

2-Only protocols that support the same stack are redistributed

-IP RIP AND OSPF

-IPX RIP cannot with OSPF

-IP EIGRP cannot with IPX EIGRP or Apple Talk EIGRP

3-Redistribution occur automatically between:

- IGRP & EIGRP if both in same AS

- Static into RIP

- Connected into any protocol using network command

4-Redistribution of classless updates to a classfull protocol could cause problems

12(config)#router <redistributing protocol>

(config-router)#redistribute <redistributed protocol> [process id] [metric <seed metric>] ! Initial ! Initial metric for redistributed routesmetric for redistributed routes!!

[match {internal/external 1/extenal 2}] ! If OSPF is redistributed: match O, OIA to be redistributed! If OSPF is redistributed: match O, OIA to be redistributed

or match OE1 to be redistributedor match OE1 to be redistributed

or match OE2 to be redistributed !or match OE2 to be redistributed !

[metric-type {1/2}] ! M! Metric type for redistributed routes into OSPF!etric type for redistributed routes into OSPF!

[subnets] ! ! Consider subnets for redistribution into OSPF!Consider subnets for redistribution into OSPF!

{level-1/level-1-2/level-2} ! If IS-IS is redistributing: ! If IS-IS is redistributing:

redistribute routes to IS-IS as iL1 or iL2 (default is iL2)redistribute routes to IS-IS as iL1 or iL2 (default is iL2)

If IS-IS is redistributed: If IS-IS is redistributed:

redistribute iL1 routes or iL2 routes or both !redistribute iL1 routes or iL2 routes or both !

[route-map <map name>] ! use route filter with redistribution !! use route filter with redistribution !

[tag <tag name>] ! ! Set tag for routes redistributed !Set tag for routes redistributed !

13Redistributing into RIPRedistributing into RIP

Redistributing into OSPFRedistributing into OSPF

• Default metric is 20.

• Default metric type is 2.

• Subnets do not redistribute by default.

14

Redistributing into IS-ISRedistributing into IS-IS

• Routes are introduced as level 2 with a metric of 0 by default.

Redistributing into EIGRPRedistributing into EIGRP

• Bandwidth in kilobytes = 10000

• Delay in 10s of microseconds = 100

• Reliability = 255 (maximum)

• Load = 1 (minimum)

• MTU = 1500 bytes

metric 10metric 10

15Example: Before RedistributionExample: Before Redistribution

B Routing TableB Routing Table

ForForRedistributionRedistribution

Ospf1Ospf1

R 10.0.0.8

16Example: Routing Tables after Route RedistributionExample: Routing Tables after Route Redistribution

Example: Routing Tables after Summarizing Routes and Example: Routing Tables after Summarizing Routes and RedistributionsRedistributions

R 10.0.0.8

17

EIGRPEIGRP IS-ISIS-IS

ExampleExample• For the shown diagram perform the following:1-Redistribute routes of the EIGRP domain as IS-IS level 1 routes with

default seed metric2-Redistribute Level 2 routes of the IS-IS domain as EIGRP routes with

seed metric (BW=10Mbps, delay=100micro seconds, reliability=255, load=1, MTU=1500byte)

SolutionSolution(config)#interface ……(config-if)#ip router isis(config-if)#end(config)#router isis(config-router)#net 49.0001.xxx……(config-router)#redistribute eigrp 100 level-1(config-router)#redistribute connected level-1(config)#router eigrp 100(config-router)#network ………(config-router)#redistribute isis level-2 metric 10000 10 255 1 1500(config-router)#end#copy run start