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| 5.4 |  | Troubleshooting RIP |
| 5.4.1 |  | Incompatible RIP version types |

When RIP is configured on a router, by default, the software receives RIP Version 1 (RIP v1) and RIP Version 2 (RIP v2) packets, but sends only RIP v1 packets. To send and receive only RIP v1 packets, the router must be configured with the command version 1 under router rip. To send and receive only RIP v2 packets, the router must be configured with the command version 2 under router rip. When the version command is used, by default, updates from other routers sending other than the specified version are ignored.

This example shows two routers running RIP between each other.

Debugs and Verification
Figure shows the configuration of router R2. In this configuration, RIP is configured to send and receive only Version 1 packets. The default RIP configuration, without the version 1 command, will allow the router to receive both Version 1 and 2 packets.

Figure shows the output of the debug ip rip command. This command reveals that router R2 is receiving a RIP packet from router R1, which is configured to send Version 2 updates.

Figure shows the output of the show ip protocols command, which indicates that the Ethernet 0 interface is sending and receiving RIP v1 packets. This means that if a Version 2 packet is received on Ethernet 0 of R2, it will be ignored because the interface can send and receive only Version 1 packets.

Figure shows the configuration of router R1. This shows that the sender R1 is configured to only send and receive Version 2 packets.

Figure shows the output of the show ip protocols command, which shows that sender R1 is sending and receiving only Version 2 packets. This is because of the version 2 command that is configured under router RIP.

Solution
An obvious solution is to configure all routers to run RIP v2. However, there may be times when this is not possible, and some routers can only run RIP v1. Therefore, another solution is to configure the appropriate interfaces to send and receive the appropriate RIP v1 or RIP v2 packets.

If the receiver, R2, is configured to receive only RIP v1 packets, it will ignore the RIP v2 updates. Router R1 must be configured on the sender side so that it will send both Version 1 and Version 2 packets. When R2 receives the Version 1 packet, it will install the routes in the routing table. R2 will ignore RIP v2 packets because it is configured for RIP v1.

Figure shows the new configuration for R1. In this configuration the sender, the R1 Ethernet 0 interface, is configured to send and receive both RIP v1 and RIP v2 packets.

Figure shows the output of show ip protocols, which indicates that the Ethernet 0 interface is sending and receiving Version 1 and Version 2 packets. The advantage to sending both Version 1 and Version 2 updates is that, if any devices on this Ethernet segment are running Version 1 only or Version 2 only, those devices will be capable of communicating with router R1 on this Ethernet segment.

Figure shows router R2 routing table after the configuration change.