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Chapter 7

RIP version 2

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RIPv1 LimitationsRIPv1: Topology Limitations

RIPv1: Discontiguous Networks

RIPv1: No VLSM Support

RIPv1: No CIDR Support

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3

RIPv1: Distance Vector, Classfull Routing Protocol

RIP Version 2 (RIPv2) is defined in RFC 1723.

RIPv2 is the first classless routing protocol discussed in this book. RIPv2 has lost popularity when compared to other routing protocols

such as EIGRP, OSPF and IS-IS.

RIPv2, it is ideal for explaining the differences between a classful

routing protocol (RIPv1) and a classless routing protocol (RIPv2).

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4

RIPv1 and RIPv2

RIPv2 is actually an enhancement of RIPv1s features and extensionsrather than an entirely new protocol.

Next-hop addressesincluded in the routing updates

Use of multicast addressesin sending updates

Authenticationoption available

Both versions of RIP share the following features and limitations:

Use of hold-down and other timersto help prevent routing loops

Use of split horizon to also help prevent routing loops

Use of triggered updateswhen there is a change in the topology forfaster convergence

Maximum hop count of 15 hops, with the hop count of 16 signifyingan unreachable network

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5

In a discontiguous network, a classful major network address, such as

172.30.0.0/16, is separated by one or more other major networks.

172.30.0.0/16 is divided by the networks:

209.165.200.228/30

209.165.200.232/30

Classful routing protocols do not include enough routing informationto

route properly for discontiguous networks.

RIPv1 Limitations

172.30.0.0

/16

172.30.0.0

/16

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R2: static summary route to the 192.168.0.0/16 network.

Redistr ibut ion- Inject static route(s) into routing protocol updates.

Summary Route

172.30.0.0/16

172.30.0.0

/16

R2(config)# ip route 192.168.0.0 255.255.0.0 null0

R2(config-router)#redistribute static

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VLSM

R3: 172.30.200.0/24 subnetted again, using the first 4 bits for

subnets and the last 4 for hosts.

172.30.200.16/28 and172.30.200.32/28

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Loop back inter face

Software-only interface Used to emulate an interface.

Can be assigned an IP address.

Specific purposes with some routing protocols such as OSPF (later)

A loopback interface can be:

pinged

subnet advertised in routing updates. Ideal for simulating multiple networks attached to the same router.

Loopback Interfaces

172.30.0.0/16

172.30.0.0

/16

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RIPv1 Topology Limitations

RIPv1 configuration for all three routers

R1(config)# router rip

R1(config-router)# network 172.30.0.0R1(config-router)# network 209.165.200.0



R2(config-router)# redistribute static

R2(config-router)# network 10.0.0.0





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Static Routes and

Null Interfaces

CIDRallows route aggregation.

A single high-level route entry with a subnet mask less than the classfulmask can be used to represent many lowerlevel routes.

This results in fewer entries in the routing table.

The static route on R2 is using a /16 mask to summarize all 256 networksranging from 192.168.0.0/24 to 192.168.255.0/24.

For Lab purposes:

The static summary route 192.168.0.0/16 does not actually exist. To simulate this static route, we will use a nu l l inter face as the exit

interface.

You do not need to enter commands to create or configure the nullinterface.

It is always up but does not forward or receive traffic.

Traffic sent to the null interface is discarded.

R2(config)# ip route 192.168.0.0 255.255.0.0 Null0

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Route Redistribution

Redistributioninvolves taking the routes from one routing source andsending those routes to another routing source.

Routes can only be redistributed into a dynamic routing protocol.

Dynamic routing protocolto a different dynamic routing protocol.

Static routesto a dynamic routing protocol.

Directly connected networksto a dynamic routing protocol.

Want R2 to redistribute our static route (192.168.0.0/16) by importing theroute into RIPv1 and then sending it to R1 and R3 using the RIPv1 process.

R2(config)# ip route 192.168.0.0

255.255.0.0 null0R2(config)# router rip


Is static route being sent via RIPv1 with other RIPv1 routes?

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13

Verifying and Testing

Connectivity

Whenever R2 pings any of the 172.30.0.0 subnets on R1 or R3, only

about 50 percent of the pings are successful.

R2#ping 172.30.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.30.1.1, timeout is 2 seconds:

!U!.!

Success rate is 60 percent (3/5), round-trip min/avg/max = 28/29/32 ms

R2#ping 172.30.100.1



!U!.!Success rate is 60 percent (3/5), round-trip min/avg/max = 28/28/28 ms

R2#

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Connectivity

R1 is able to ping 10.1.0.1 but is unsuccessful when attempting to

ping the 172.30.100.1 interface on R3.

R1#ping 10.1.0.1



!!!!!

Success rate is 100 percent (5/5),round-trip min/avg/max = 28/28/28 ms

R1#ping 172.30.100.1



.....Success rate is 0 percent (0/5)

R1#

X

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Connectivity

R3 is able to ping 10.1.0.1 but is unsuccessful when attempting toping the 172.30.1.1 interface on R1.

As you can see, there is an obvious problem when trying tocommunicate with the 172.30.0.0 discontiguous subnets.

R3#ping 10.1.0.1



!!!!!

Success rate is 100 percent (5/5),round-trip min/avg/max = 28/28/28 ms

R3#ping 172.30.1.1



.....Success rate is 0 percent (0/5)

R3#

X

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RIPv1 on both Routers R1 and R3 will summarize their 172.30.0.0

subnets to the classful major network address of 172.30.0.0 when

sending routing updates to R2.

RIPv1:

Discontiguous

Networks

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Examining the Routing Tables

R2 has two equal-cost routes to the 172.30.0.0/16 network. R1 and R3 are sending R2 a RIPv1 update for the 172.30.0.0 network

with a metric of 1 hop.

R2s routing table only contains the major classful network address of

172.30.0.0 and adds the Class B subnet mask of /16.

R2# show ip route

R 172.30.0.0/16 [120/1] via 209.165.200.230, 00:00:09, Serial0/0/0

[120/1] via 209.165.200.234, 00:00:11, Serial0/0/1

209.165.200.0/30 is subnetted, 2 subnets

C 209.165.200.232 is directly connected, Serial0/0/1

C 209.165.200.228 is directly connected, Serial0/0/010.0.0.0/16 is subnetted, 1 subnets

C 10.1.0.0 is directly connected, FastEthernet0/0

S 192.168.0.0/16 is directly connected, Null0

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debug ip rip

R2 is receivingtwo 172.30.0.0 equal-cost routeswith a metric of 1 hop:

one route on Serial 0/0/0 from R1 and

the other route on Serial 0/0/1 from R3.

Also noticethat the subnet mask is not includedwith the networkaddress in the update.

R2# debug ip rip

RIP: receivedv1 update from 209.165.200.230 onSerial0/0/0

172.30.0.0 in 1 hops

RIP: receivedv1 update from 209.165.200.234 onSerial0/0/1

172.30.0.0 in 1 hops

RIP: sending v1 update to 255.255.255.255 via Serial0/0/0

(209.165.200.229)

RIP: build update entries

network 10.0.0.0 metric 1

subnet 209.165.200.232 metric 1


(209.165.200.233)


network 10.0.0.0 metric 1subnet 209.165.200.228 metric 1

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show ip route

R1 has its own 172.30.0.0 routes: 172.30.2.0/24

172.30.1.0/24.

R1 does not send R2 those subnets.

R1 and R3 are boundary routers only sending the summarized 172.30.0.0

Result, R2 only knows about the 172.30.0.0/16 classful network and is

unaware of any 172.30.0.0 subnets.

R1# show ip route


C 172.30.2.0 is directly connected, Loopback0



R 209.165.200.232 [120/1] via 209.165.200.229, 00:00:16,Serial0/0/0C 209.165.200.228 is directly connected, Serial0/0/0

R 10.0.0.0/8 [120/1] via 209.165.200.229, 00:00:16, Serial0/0/0

R1#

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How Classful Routing

Protocols Determine

Subnet Masks

172.30.0.0 172.30.0.0

Apply classful

default mask of /16

Apply classful

default mask of /16

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Protocols Determine

Subnet Masks

10.0.0.0

Apply

classful

default

mask of /8

Apply

classful

default mask

of /8

10.0.0.0

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Protocols Determine

Subnet Masks

172.30.2.0

172.30.110.0

172.30.1.0

172.30.100.0172.30.200.16

172.30.200.32

172.30.0.0

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RIPv1: No VLSM Support

Because RIPv1 does not send the subnet mask in routing updates, itcannot support VLSM.

The R3 router is configured with the following VLSM subnets, all ofwhich are members of the Class B network 172.30.0.0/16:

172.30.100.0/24 (FastEthernet 0/0)

172.30.110.0/24 (Loopback 0)

172.30.200.16/28 (Loopback 1)

172.30.200.32/28 (Loopback 2)

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We see the static route, lets see if it is be sent in RIPv1 updates

with the other RIPv1 routes






R2(config-router)# end

R2# show ip route

R 172.30.0.0/16 [120/1] via 209.165.200.230, 00:00:09, Serial0/0/0

[120/1] via 209.165.200.234, 00:00:11, Serial0/0/1







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R1 Routing Table

Notice that R1 is not receiving this 192.168.0.0/16 routein its RIPupdates from R2

R1# show ip route






R 10.0.0.0/8 [120/1] via 209.165.200.229, 00:00:16, Serial0/0/0

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debug ip rip

R2 is not including the 192.168.0.0/16 route in its RIPv1 updates

to either R1 or R3.

R2# debug ip rip

RIP: received v1 update from 209.165.200.230 on Serial0/0/0

172.30.0.0 in 1 hops


172.30.0.0 in 1 hops


(209.165.200.229)


network 10.0.0.0 metric 1

subnet 209.165.200.232 metric 1


(209.165.200.233)


network 10.0.0.0 metric 1subnet 209.165.200.228 metric 1

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The static route 192.168.0.0 has a /16 mask.

This is fewer bits than the classful Class C mask of /24.

RIPv1 and other c lassfu l ro ut ing protoco ls cannot supp or t CIDR

routes that are summarized routes w ith a smaller subnet mask than

the classful mask o f the route.

RIPv1 ignores these supernets in the routing table and does not include

them in updates to other routers.

This is because the receiv ing router wo uld on ly be able to apply the

larger /24 classfu l mask to th e update and no t the shorter /16 mask.

Note:

If the 192.168.0.0 static route were configured with a /24 mask or

greater, this route would be included in the RIP updates.

The receiving routers would apply the classful /24 mask to this update.




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Configuring RIPv2

Enabling and Verifying RIPv2

Auto-Summary and RIPv2

Disabling Auto-Summary in RIPv2

Verifying RIPv2 Updates

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Configuring RIPv2

Configuring RIPv2 is

similar to configuringRIPv1, with the addition

of a single RIPcommand, version 2.

Although RIPv2 uses the

same basicconfiguration

commandsas RIPv1,

the results of using

RIPv2 are different,

allowing both CIDR andVLSM to be used in the

network.

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Default RIPv1: When configuring RIP

Router only sends RIPv1 messages, it can process both RIPv1 and

RIPv2 messages. Ignore the RIPv2 fields in the route entry.

RIPv2 will ignore RIPv1 updates.

R2# show ip protocols

Default version control: send version 1, receive any version

Interface Send Recv Triggered RIP Key-chain

Serial0/0/0 1 1 2

Serial0/0/1 1 1 2

Automatic network summarization is in effect

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version 2command is used to modify RIP to use Version 2.

This command should be configured on all routers in the routing

domain.


R1(config-router)# version 2



R3(config)# router ripR3(config-router)# version 2

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Routing Protocol is rip

Sending updates every 30 seconds, next due in 1 seconds

Invalid after 180 seconds, hold down 180, flushed after 240

Outgoing update filter list for all interfaces is

Incoming update filter list for all interfaces is

Redistributing: static, ripDefault version control: send version 2, receive version 2


Serial0/0/0 2 2

Serial0/0/1 2 2


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Restoring RIP to Version 1

Default behavior of RIPv1 can be restored by using either the

(slightly different behaviors in sending and receiving):

version 1 command

no version command

If done, should be configured on all routers.



!or


R1(config-router)# no version

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You still see the summarized 172.30.0.0/16 routewith the same

two equal-cost paths.

R2# show ip route

R 172.30.0.0/16 [120/1] via 209.165.200.230, 00:00:28, Serial0/0/0

[120/1] via 209.165.200.234, 00:00:18, Serial0/0/1



C 209.165.200.228 is directly connected, Serial0/0/010.0.0.0/16 is subnetted, 1 subnets



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Routers R1 and R3 still do not include the 172.30.0.0 subnetsof theother router.

The only difference so farbetween RIPv1 and RIPV2 is that R1 and R3each have a route to 192.168.0.0/16.

This route was the (CIDR) static route configured on R2 and redistributed byRIP.

Whats happening?

R1# show ip route


C 172.30.2.0 is directly connected, Loopback0




R 10.0.0.0/8 [120/1] via 209.165.200.229, 00:00:04, Serial0/0/0

R 192.168.0.0/16 [120/1] via 209.165.200.229, 00:00:04, Serial0/0/0

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Notice that RIPv2 is sending both the network address and

subnet mask.

Notice that the route sent is the summarized classful network

address, 172.30.0.0/16

not the individual 172.30.1.0/24 and 172.30.2.0/24 subnets.

R1# debug ip rip

RIP: sending v2 updateto 224.0.0.9 via Serial0/0/0

(209.165.200.230)


172.30.0.0/16 via 0.0.0.0, metric 1, tag 0


10.0.0.0/8 via 0.0.0.0 in 1 hops

192.168.0.0/16 via 0.0.0.0 in 1 hops

209.165.200.232/30 via 0.0.0.0 in 1 hops

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By default , RIPv2 autom atical ly summarizes network s at majornetwo rk b oundar ies, just l ike RIPv1.

Both R1 and R3 routers are still summarizing their 172.30.0.0

subnets to the Class B address of 172.30.0.0 when sending updates

out their interfaces on the 209.165.200.228 and 209.165.200.232

networks, respectively.



Default version control: send version 2, receive version 2


FastEthernet0/0 2 2

FastEthernet0/1 2 2Serial0/1/0 2 2


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Disabling Auto-summary in RIPv2

To modify the default RIPv2 behavior of automatic summarization,

use the no auto-summary command


R2(config-router)# no auto-summary


R3(config-router)# no auto-summary

R1(config)# router ripR1(config-router)# no auto-summary


Automatic network summarization is not in effect

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The routing table for R2 now contains the individual subnets for 172.30.0.0/16.

Notice that a single summary route with two equal-cost paths no longer exists.

Each subnet and mask has its own specific entry, along with the exit interface andnext-hop address to reach that subnet.

R2# show ip route

172.30.0.0/16 is variably subnetted, 6 subnets, 2 masks

R 172.30.200.32/28 [120/1] via 209.165.200.234, 00:00:09, Serial0/0/1

R 172.30.200.16/28 [120/1] via 209.165.200.234, 00:00:09, Serial0/0/1

R 172.30.2.0/24 [120/1] via 209.165.200.230, 00:00:03, Serial0/0/0

R 172.30.1.0/24 [120/1] via 209.165.200.230, 00:00:03, Serial0/0/0

R 172.30.100.0/24 [120/1] via 209.165.200.234, 00:00:09, Serial0/0/1

R 172.30.110.0/24 [120/1] via 209.165.200.234, 00:00:09, Serial0/0/1




10.0.0.0/16 is subnetted, 1 subnetsC 10.1.0.0 is directly connected, FastEthernet0/0


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Fully converged routing tables.

R1# show ip route


R 172.30.200.32/28 [120/2] via 209.165.200.229, 00:00:01, Serial0/0/0

R 172.30.200.16/28 [120/2] via 209.165.200.229, 00:00:01, Serial0/0/0

C 172.30.2.0/24 is directly connected, Loopback0

C 172.30.1.0/24 is directly connected, FastEthernet0/0R 172.30.100.0/24 [120/2] via 209.165.200.229, 00:00:01, Serial0/0/0

R 172.30.110.0/24 [120/2] via 209.165.200.229, 00:00:01, Serial0/0/0


R 209.165.200.232 [120/1] via 209.165.200.229, 00:00:02, Serial0/0/0



R 10.1.0.0 [120/1] via 209.165.200.229, 00:00:02, Serial0/0/0

R 192.168.0.0/16 [120/1] via 209.165.200.229, 00:00:02, Serial0/0/0

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Verifying RIPv2 UpdatesR2# debug ip rip

RIP: receivedv2update from 209.165.200.234 on Serial0/0/1

172.30.100.0/24 via 0.0.0.0 in 1 hops

172.30.110.0/24 via 0.0.0.0 in 1 hops

172.30.200.16/28 via 0.0.0.0 in 1 hops

172.30.200.32/28 via 0.0.0.0 in 1 hops

RIP: sendingv2update to 224.0.0.9 via Serial0/0/0

(209.165.200.229)


10.1.0.0/16 via 0.0.0.0, metric 1, tag 0

172.30.100.0/24 via 0.0.0.0, metric 2, tag 0

172.30.110.0/24 via 0.0.0.0, metric 2, tag 0

172.30.200.16/28 via 0.0.0.0, metric 2, tag 0

172.30.200.32/28 via 0.0.0.0, metric 2, tag 0

192.168.0.0/16 via 0.0.0.0, metric 1, tag 0

209.165.200.232/30 via 0.0.0.0, metric 1, tag 0

Sending and receiving routing updates, which are individual routes with their

subnet mask instead of a single summary route with the classful mask.

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Notice also that the updates are sent using the multicast address

224.0.0.9.

RIPv1sends updates as a broadcast 255.255.255.255. In general multicast updates:

Take up less bandwidthon the network.

Require less processingby devices that are not RIP enabled.

R2# debug ip rip

RIP: sendingv2update to 224.0.0.9via Serial0/0/0

(209.165.200.229)

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Verifying and Troubleshooting

RIPv2Verification and Troubleshooting Commands

Common RIPv2 Issues

Authentication

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show ip route Command

Firstcommand to use to check for network convergence.

Important to look for the routes that you expect to be in the

rout in g table as wel l as for those that shou ld no t be in the

rout ing table.

R1# show ip route


R 172.30.200.32/28 [120/2] via 209.165.200.229, 00:00:01, Serial0/0/0

R 172.30.200.16/28 [120/2] via 209.165.200.229, 00:00:01, Serial0/0/0

C 172.30.2.0/24 is directly connected, Loopback0

C 172.30.1.0/24 is directly connected, FastEthernet0/0

R 172.30.100.0/24 [120/2] via 209.165.200.229, 00:00:01, Serial0/0/0R 172.30.110.0/24 [120/2] via 209.165.200.229, 00:00:01, Serial0/0/0


R 209.165.200.232 [120/1] via 209.165.200.229, 00:00:02, Serial0/0/0



R 10.1.0.0 [120/1] via 209.165.200.229, 00:00:02, Serial0/0/0

R 192.168.0.0/16 [120/1] via 209.165.200.229, 00:00:02, Serial0/0/0

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show ip interface brief Command

If a network is missingfrom the routing table, it is often becausean interface is down or incorrectly configured.

The show ip interface briefcommand quickly verifies the

status of all interfaces.

R1# show ip interface brief

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 172.30.1.1 YES NVRAM up up

FastEthernet0/1 172.30.2.1 YES NVRAM up up

Serial0/0/0 209.165.200.230 YES NVRAM up up

Serial0/0/1 unassigned YES NVRAM down down

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show ip protocols Command

The show ip protocolscommand verifies several critical items,including whether RIP is enabled, the version of RIP, the status ofautomatic summarization, and the networks that were included in thenetworkstatements.



Sending updates every 30 seconds, next due in 29 seconds

Invalid after 180 seconds, hold down 180, flushed after 240

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

Redistributing: rip

Default version control: send version 2, receive version 2


FastEthernet0/0 2 2

FastEthernet0/1 2 2

Serial0/0/0 2 2

Automatic network summarization is not in effect

Maximum path: 4

Routing for Networks:

172.30.0.0

209.165.200.0

Routing Information Sources:Gateway Distance Last Update

209.165.200.229 120 00:00:18

Distance: (default is 120)

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debug ip rip Command

debug ip rip is an excellent command to use to examine the contents of the routingupdates that are sent and received by a router.

There can be times when a route is received by a router but is not added to therouting table.

One reason for this could be that a static route is also configured for the sameadvertised network.

R2# debug ip rip


172.30.100.0/24 via 0.0.0.0 in 1 hops

172.30.110.0/24 via 0.0.0.0 in 1 hops

172.30.200.16/28 via 0.0.0.0 in 1 hops

172.30.200.32/28 via 0.0.0.0 in 1 hops

RIP: sending v2 update to 224.0.0.9 via Serial0/0/0 (209.165.200.229)


10.1.0.0/16 via 0.0.0.0, metric 1, tag 0

172.30.100.0/24 via 0.0.0.0, metric 2, tag 0

172.30.110.0/24 via 0.0.0.0, metric 2, tag 0

172.30.200.16/28 via 0.0.0.0, metric 2, tag 0

172.30.200.32/28 via 0.0.0.0, metric 2, tag 0

192.168.0.0/16 via 0.0.0.0, metric 1, tag 0

209.165.200.232/30 via 0.0.0.0, metric 1, tag 0

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ping Command

An easy way to verify round-trip connectivity is with theping

command

R2#ping 172.30.2.1



!!!!!


R2#ping 172.30.100.1


Sending 5, 100-byte ICMP Echos to 172.30.100.1, timeout is 2 seconds:!!!!!


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show running-config CommandR1# show running-config

!

hostname R1!

interface FastEthernet0/0

ip address 172.30.1.1 255.255.255.0

!

interface FastEthernet0/1

ip address 172.30.2.1 255.255.255.0

!

interface Serial0/0/0

ip address 209.165.200.230 255.255.255.252

clock rate 64000

!

router rip

version 2

network 172.30.0.0

network 209.165.200.0

no auto-summary

!

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Authentication

It is good practice to authenticate routing information.

RIPv2, EIGRP, OSPF, IS-IS, and Border Gateway Protocol (BGP)can be configured to encrypt and authenticate routing information.

Hides the content of the routing information

Routers will only accept routing information from otherrouters that have been configured with the same password

ccnaexp7

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