You want to use the more flexible features of RIP Version 2.
By default, Cisco routers will listen for both RIP Version 1 and 2 packets, but they will only send Version 1. If you want to configure the router to send and receive only Version 2 RIP packets, use the version 2 configuration command:
Router2#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router2(config)#router rip Router2(config-router)#version 2 Router2(config-router)#network 172.25.0.0 Router2(config-router)#network 192.168.30.0 Router2(config-router)#end Router2#
You can also enable RIP Version 2 sending and receiving separately for individual interfaces:
Router1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router1(config)#interface Serial0/0.2
Router1(config-subif)#ip rip send version 2
Router1(config-subif)#ip rip receive version 2
Router1(config-subif)#end
Router1#
By default, the router will listen for Version 1 and 2 packets but it will only send Version 1. You can run both versions simultaneously on the same interface. However, the router will then have to transmit all updates using both versions, which can cause an unnecessary burden both for the router and the network. In general, RIP Version 2 is preferred, particularly because of the support for modern IP features such as variable-length subnet masks:
Router2#show ip protocols
Routing Protocol is "rip"
Sending updates every 60 seconds, next due in 19 seconds
Invalid after 180 seconds, hold down 0, flushed after 240
Output delay 10 milliseconds between packets
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
Interface Send Recv Triggered RIP Key-chain
Ethernet0 2 2
Serial0.1 2 2 Yes
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
172.25.0.0
192.168.30.0
Routing Information Sources:
Gateway Distance Last Update
172.25.2.1 120 01:04:31
Distance: (default is 120)
Router2#
This command shows that the router is sending and receiving only Version 2 on both interfaces. In this case, the router will reject any incoming RIP Version 1 packets on either of these ports. So you need to make sure that the neighboring routers on these interfaces are also running Version 2.
The second configuration example leaves the default configuration for all of the interfaces except Serial0/0.2, which sends and receives only RIP Version 2:
Router1#show ip protocols
Routing Protocol is "rip"
Sending updates every 30 seconds, next due in 11 seconds
Invalid after 180 seconds, hold down 0, flushed after 240
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Redistributing: static, rip
Default version control: send version 1, receive any version
Interface Send Recv Triggered RIP Key-chain
Serial0/0.2 2 2 Yes
FastEthernet0/1 1 1 2
Automatic network summarization is in effect
Maximum path: 4
Routing for Networks:
172.22.0.0
172.25.0.0
Routing Information Sources:
Gateway Distance Last Update
172.25.2.2 120 14:40:28
172.22.1.4 120 01:06:11
Distance: (default is 120)
Router1#
Debug traces show which version the router sends and receives for every update:
Router2#debug ip rip RIP protocol debugging is on Router2# Aug 11 14:38:54: RIP: received v2 update from 172.25.2.1 on Serial0.1 Aug 11 14:38:54: 0.0.0.0/0 via 0.0.0.0 in 1 hops Aug 11 14:38:54: 172.22.0.0/16 via 0.0.0.0 in 1 hops Aug 11 14:38:54: 172.25.0.0/16 via 0.0.0.0 in 1 hops Aug 11 14:38:54: 172.25.1.0/24 via 0.0.0.0 in 1 hops Aug 11 14:38:54: 172.25.25.1/32 via 0.0.0.0 in 1 hops Aug 11 14:38:57: RIP: sending v2 update to 224.0.0.9 via Serial0.1 Aug 11 14:38:57: RIP: build update entries Aug 11 14:38:57: 172.25.25.2/32 via 0.0.0.0, metric 1, tag 0 Aug 11 14:38:57: 192.168.30.0/24 via 0.0.0.0, metric 11, tag 0 Router2#
If you configure a router to listen only for one version, however, it will just drop any packets of the other version that it receives:
Router2#debug ip rip RIP protocol debugging is on Router2# Aug 11 14:43:11: RIP: ignored v1 packet from 172.25.2.1 (illegal version) Aug 11 14:43:11: RIP: received v2 update from 172.25.2.1 on Serial0.1
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