Chapter 5 RIP Version 1

© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicITE I Chapter 6 1

RIPv1 & RIPv2

Routing Protocols and Concepts – Chapter 5

© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicITE 1 Chapter 6 2

IntroductionDifference between RIPv1 & RIPv2

RIPv1-A classful distance vector routing protocol-Does not support discontiguous subnets-Does not support VLSM-Does not send subnet mask in routing update-Routing updates are broadcast

RIPv2

-A classless distance vector routing protocol that is an enhancement of RIPv1’s features.

-Next hop address is included in updates

-Routing updates are multicast

-The use of authentication is an option


Introduction

Similarities between RIPv1 & RIPv21. Use of holddown timers to prevent routing loops2. Use of split horizon or split horizon with poison

reverse also to prevent routing loops3. Use of triggered updates when there is a change in

the topology for faster convergence.4. Maximum hop count of 15


RIP Message Formats Comparing RIPv1 & RIPv2 Message FormatsRIPv2 Message format is similar to RIPv1 but has 2 extensions

1st extension is the subnet mask field

2nd extension is the addition of next hop address


RIPv1 Operation

RIP uses 2 message types:1. Request message

-This is sent out on startup by each RIP enabled interface

-Requests all RIP enabled neighbors to send routing table

2. Response message

-Message sent to requesting router containing routing table


RIP- Administrative DistanceRIP’s default administrative distance is 120


Basic RIPv1 Configuration A topology used to configure RIPv1.


Basic RIPv1 Configuration To enable RIP enter:

-Router rip at the global configuration prompt

-Prompt will look like R1(config-router)#


Basic RIPv1 Configuration

Specifying Networks, Use the network command to:

2. Enable RIP on all interfaces that belong to this network

3. Advertise this network in RIP updates sent to other routers every 30 seconds


Configuring RIPv2

Configuring RIP on a Cisco router (By default it is running RIPv1)

Configuring RIPv2 on a Cisco router

-Requires using the version 2 command

-RIPv2 ignores RIPv1 updates

To verify RIPv2 is configured use the show ip protocols command


Configuring RIPv2


Verification and Troubleshooting

Use the following commands:

show ip route show ip protocols

debug ip rip


Verification and Troubleshooting

show ip protocols -Displays routing protocol

configured on router


Verification and Troubleshooting Debug ip rip command -Used to display RIP routing

updates as they are happening


Passive interface –RIPv1Sending out unneeded updates on a LAN impacts the network

in three ways:

1. Bandwidth is wasted transporting unnecessary updates. Because RIP updates are broadcast, switches will forward the updates out all ports.

2. All devices on the LAN must process the update up to the Transport layers, where the receiving device will discard the update.

3. Advertising updates on a broadcast network is a security risk. RIP updates can be intercepted with packet sniffing software. Routing updates can be modified and sent back to the router.


Passive interface –RIPv1 Passive interface command used to prevent a router from

sending updates through an interface

-Example:

Router(config-router)#passive-interface interface-type interface-number


Automatic Summarization – RIPv1


Automatic Summarization – RIPv1 Summarization: Consolidation of networks and advertised in

classful network advertisements. In rip this classful a single summary route to be advertised to others routers.

The original scenario has been modified such that:Three classful networks are used:

172.30.0.0/16192.168.4.0/24192.168.5.0/24

The 172.30.0.0/16 network is subnetted into three subnets:172.30.1.0/24172.30.2.0/24172.30.3.0/24

The following devices are part of the 172.30.0.0/16 classful network address:

All interfaces on R1S0/0/0 and Fa0/0 on R2


Automatic Summarization – RIPv1

Boundary Routers

RIP automatically summarizes classful networks

Boundary routers summarize RIP subnets from one major network to another.


Automatic Summarization – RIPv1 RIP uses automatic summarization to reduce the size

of a routing table.


Automatic Summarization – RIPv1 Advantages of automatic summarization:

-The size of routing updates is reduced

-Single routes are used to represent multiple routes which results in faster lookup in the routing table.


Automatic Summarization – RIPv1 Disadvantage of Automatic Summarization:

-Does not support discontiguous networks


Auto-Summary & RIPv2

RIPv2 will automatically summarize routes at major network boundaries and can also summarize routes with a subnet mask that is smaller than the classful subnet mask


Disabling Auto-Summary in RIPv2

To disable automatic summarization issue the no auto-summary command




When using RIPv2 with automatic summarization turned off, RIPv2 will no longer summarize networks to their classful address at boundary routers. RIPv2 will now include all subnets and their appropriate masks in its routing updates.

The command show ip protocols can be used to verify that "automatic network summarization is not in effect."


Default Route and RIPv1



To provide Internet connectivity to all other networks in the RIP routing domain, the default static route needs to be advertised to all other routers that use the dynamic routing protocol.

We could configure a static default route on R1 pointing to R2, but this technique is not scalable. So we need propagating the Default Route in RIPv1.

Default-information originate command -This command is used to specify that the router is to originate default information, by propagating the static default route in RIP update.




VLSM & CIDR

RIPv2 and VLSM

Networks using a VLSM IP addressing scheme

Use classless routing protocols (i.e. RIPv2) to disseminate

network addresses and their subnet

masks


Remove RIPTo remove the RIP routing process use the following command no router rip


Summary

YesYesYesYesYesYesYesYesYesRIPv2

NoNoNoYesYesYesYesNoYesRIPv1

Uses Authen-tication

SupportsVLSM

SupportCIDR

AutoSummary

MaxHop

count= 15

Use ofSplit

Horizon or

Split Horizon

w/Poison

Reverse

UsesHold-DownTimers

ClasslessRoutingProtocol

DistanceVector

RoutingProtocol


Summary: Commands used by RIP

Used to display timers used by RIPRtr#show ip protocols

Used by RIP to propagate default routesRtr(config-router)#default-information originate

Prevent RIP updates from going out an interfaceRtr(config-router)#passive-interface fa0/0

used to view real time RIP routing updatesRtr#debug ip rip

Associates a network with a RIP routing processRtr(config-router)#network

Enables RIP routing processRtr(config)#router rip

Command’s purposeCommand


Chapter 5 RIP Version 1

Documents

cisco systems

cisco public

cisco router

ripv1 ripv2 ripv1

ripv2 ite

ripv1 ripv2 routing

ripv1 updates

router ite