19. RIPv2

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Enabling RIP

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Routing protocols

are used betweenrouters to determinepaths and maintainrouting tables. After the path isdetermined, a router

can route a routedprotocol.

What Is a Routing Protocol?

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An autonomous system is a collection of networks under acommon administrative domain. IGPs operate within an autonomous system. EGPs connect different autonomous systems.

Autonomous Systems: Interior orExterior Routing Protocols

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Classes of Routing Protocols

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Administrative Distance:Ranking Routes

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Distance VectorSources of Information andDiscovering Routes

A B C

10.1.0.0 10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0

Routing Table

10.2.0.0

10.3.0.0

0

0

S0

S1

Routing Table

10.3.0.0 S0 0

10.4.0.0 E0 0

Routing Table

10.1.0.0

10.2.0.0

E0

S0

0

0

10.4.0.0

Routers discover the best path todestinations from each neighbor

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A B C

10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0

Routing Table

10.1.0.0

10.2.0.0

10.3.0.0

Routing Table

10.2.0.0

10.3.0.0

10.4.0.0

10.1.0.0

0

0

1

1

S0

S1

S1

S0

Routing Table

10.3.0.0 S0 0

10.4.0.0 E0 0

10.2.0.0 S0 1

E0

S0

S0 1

0

0

10.1.0.0 10.4.0.0


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A B C

10.1.0.0 10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0

Routing Table

10.1.0.0

10.2.0.0

10.3.0.0

10.4.0.0

Routing Table

10.2.0.0

10.3.0.0

10.4.0.0

10.1.0.0

0

0

1

1

S0

S1

S1

S0

Routing Table

10.3.0.0 S0 0

10.4.0.0 E0 0

10.2.0.0 S0

10.1.0.0 S0

1

2

E0

S0

S0

S0

1

2

0

0

10.4.0.0


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Distance VectorMaintaining RoutingInformation

A

Process toupdate this

routingtable

Topologychangecausesrouting

tableupdate

Updates proceed step-by-stepfrom router to router

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A


routingtable

Router A sendsout this updated

routing tableafter the

next periodexpires


tableupdate


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AB


routingtable


routingtable


tableupdate

Router A sendsout this updated

routing tableafter the

next periodexpires


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Maintaining Routing Information ProblemRouting Loops

A B C

10.1.0.0 10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0

RoutingTable

10.3.0.0

S0E0S0S

0

1

2

10.1.0.0

10.2.0.

0

10.4.0.0

0

0

RoutingTable

10.1.0.0

E0S0S0S

0

1

2

10.4.0.0

10.3.0.

0

10.2.0.0

0

0

RoutingTable

10.2.0.0

S0S1S1S

0

1

1

10.1.0.0

10.4.0.

0

10.3.0.0

0

0

Each node maintains the distance from itself to eachpossible destination network

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A B C

10.1.0.0 10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0X

RoutingTabl

e

10.3.0.0

S0E0S0S

0

1

2

10.1

.0.0

10.2.0.0

10.4.0.

0

0Down

RoutingTable

10.1.0.0

E0S0S0S

0

1

2

10.4

.0.0

10.3.0.0

10.2.0.

0

0

0

RoutingTabl

e

10.2.0.0

S0S1S1S

0

1

1

10.1

.0.0

10.4.0.0

10.3.0.

0

0

0

Slow convergence produces inconsistent routing

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A B C

10.1.0.0 10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0X

RoutingTabl

e

10.3.0.0

S0S0S0S

0

1

2

10.1

.0.0

10.2.0.0

10.4.0.

0

0

2

RoutingTable

10

.1.0.0

E0S0S0S

0

1

2

10.4

.0.0

10.3.0.0

10.2.0.

0

0

0

RoutingTabl

e

10.2.0.0

S0S1S1S

1

1

1

10.1

.0.0

10.4.0.0

10.3.0.

0

0

0

10.4.0.0

Router C concludes that the best path to network10.4.0.0 is through Router B

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Router A updates its table to reflect the new buterroneous hop count

A B C

10.1.0.0 10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0X

RoutingTabl

e

S0S0S0S

0

1

2

10.3.0.0

10.1

.0.0

10.2.0.0

10.4.0.

0

0

2

RoutingTable

E0S0S0S

0

1

4

10

.1.0.0

10.4

.0.0

10.3.0.0

10.2.0.

0

0

0

RoutingTable

S0S1S1S

0

3

1

10.2.0.0

10.1

.0.0

10.4.0.0

10.3.0.

0

0

0

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Symptom: Counting to Infinity

Packets for network 10.4.0.0 bounce between routers A, B, and C Hop count for network 10.4.0.0 counts to infinity

A B C

10.1.0.0 10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0X

RoutingTable

10.3.0.0

S0S0S0S

0

1

2

10.1

.0.0

10.2.0.0

10.4.0.

0

0

4

Routin

gTable

E0S0S0S

0

1

6

10

.1.0.0

10.4

.0.0

10.3.0.0

10.2.0.

0

0

0

RoutingTable

S0S1S1S

0

5

1

10

.2.0.0

10.1

.0.0

10.4.0.0

10.3.0.

0

0

0

10.4.0.0

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Solution: Defining a Maximum

Define a limit on the number of hops to prevent infinite loops

A B C

10.1.0.0 10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0X

Routing Table

10.3.0.0 S0

S0

S0

S0

1

210.1.0.0

10.2.0.0

10.4.0.0

0

16

RoutingTableE0S0S0S

0

11

6

10.1.0.010.4.0.0

10.3.0.

0

10.2.0.0

0

0

RoutingTable

S0S1S1S

0

161

10.2.0.010.1.0.0

10.4.0.

0

10.3.0.0

0

0

10.4.0.0

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Solution: Split Horizon

It is never useful to send information about a route back in the directionfrom which the original packet came

A B C

10.1.0.0 10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0X

XX

RoutingTable

10

.3.0.0

S0S0S0S

0

1

2

10.1

.0.0

10.2.0.0

10.4.0.

0

0

0

Routin

gTable

E0S0S0S

0

1

2

10

.1.0.0

10.4

.0.0

10.3.0.0

10.2.0.

0

0

0

Routin

gTable

S0S1S1E

1

1

2

10

.2.0.0

10.1

.0.0

10.4.0.0

10.3.0.

0

0

0

10.4.0.0

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Solution: Route Poisoning

A B C

10.1.0.0 10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0X

Routing Table

10.3.0.0 S0

S0

S0

S0

1

210.1.0.0

10.2.0.0

10.4.0.0

0

Infinity

RoutingTable10.1.0.0

E0S0S0S

0

1

2

10.4.

0.0

10.3.0.

0

10.2.0.0

0

0

RoutingTable

10.2.0.0

S0S1S1E

1

1

2

10.1.0.0

10.4.0.

0

10.3.0.0

0

0

10.4.0.0

Routers set the distance of routes that have gone down to infinity

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Solution: Hold-Down Timers

Router keeps an entry for the network possibly downstate, allowing time forother routers to recompute for this topology change

Network 10.4.0.0 is downthen back up

then back down

Update afterhold-down Time

Network 10.4.0.0is unreachable

A B C

10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0 XUpdate after

hold-down Time

10.4.0.0

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Solution: Triggered Updates

Router sends updates when a change in its routing table occurs

A B C

10.2.0.0 10.3.0.0

E0 S0 S0 S1 S0 E0 X




10.4.0.0

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RIPv1 and RIPv2 Comparison

RIPv1 RIPv2

Routing protocol Classful Classless

Supports variable-length subnet mask? No Yes

Sends the subnet mask along with the routingupdate?

No Yes

Addressing type Broadcast Multicast

Defined in RFC 1058RFCs 1721, 1722,

and 2453

Supports manual route summarization? No YesAuthentication support? No Yes

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Starts the RIP routing process

RouterX(config)#router rip

RouterX(config-router)# network network-number

Selects participating attached networks Requires a major classful network number

RIP Configuration

Enables RIP version 2

RouterX(config-router)# version 2

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RIP Configuration Example

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Verifying the RIP Configuration

Routing Protocol is "rip"

Sending updates every 30 seconds, next due in 6 secondsInvalid after 180 seconds, hold down 180, flushed after 240Outgoing update filter list for all interfaces is not setIncoming update filter list for all interfaces is not setRedistributing: ripDefault version control: send version 2, receive version 2Interface Send Recv Triggered RIP Key-chainFastEthernet0/0 2 2Serial0/0/2 2 2

Automatic network summarization is in effectMaximum path: 4Routing for Networks:10.0.0.0172.16.0.0Routing Information Sources:Gateway Distance Last Update10.1.1.2 120 00:00:25Distance: (default is 120)

RouterA#

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Displaying the IP Routing Table

RouterA# show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter areaN1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate defaultU - per-user static route, o - ODRT - traffic engineered route

Gateway of last resort is not set

172.16.0.0/24 is subnetted, 1 subnetsC 172.16.1.0 is directly connected, fastethernet0/010.0.0.0/24 is subnetted, 2 subnetsR 10.2.2.0 [120/1] via 10.1.1.2, 00:00:07, Serial0/0/2C 10.1.1.0 is directly connected, Serial0/0/2R 192.168.1.0/24 [120/2] via 10.1.1.2, 00:00:07, Serial0/0/2

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debug ip rip Command

RouterA# debug ip ripRIP protocol debugging is onRouterA#00:06:24: RIP: received v1 update from 10.1.1.2 on Serial0/0/200:06:24: 10.2.2.0 in 1 hops00:06:24: 192.168.1.0 in 2 hops00:06:33: RIP: sending v1 update to 255.255.255.255 via FastEthernet0/0 (172.16.1.1)

00:06:34: network 10.0.0.0, metric 100:06:34: network 192.168.1.0, metric 300:06:34: RIP: sending v1 update to 255.255.255.255 via Serial0/0/2 (10.1.1.1)00:06:34: network 172.16.0.0, metric 1

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19. RIPv2

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