Cisco IOS Cookbook, 2nd Edition

Enabling RIP Authentication

Problem

You want to authenticate your RIP traffic to ensure that unauthorized equipment cannot affect how traffic is routed through your network.

Solution

The following set of commands enables plain-text RIP authentication:

Router1#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#key chain ORA
Router1(config-keychain)#key 1
Router1(config-keychain-key)#key-string oreilly
Router1(config-keychain-key)#exit
Router1(config)#interface FastEthernet0/0.1 
Router1(config-subif)#ip rip authentication key-chain ORA
Router1(config-subif)#ip rip authentication mode text
Router1(config-subif)#exit
Router1(config)#end
Router1#

For greater security, Cisco routers can also use MD5-based authentication:

Router1#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#key chain ORA
Router1(config-keychain)#key 1
Router1(config-keychain-key)#key-string oreilly
Router1(config-keychain-key)#exit
Router1(config)#interface FastEthernet0/0.1 
Router1(config-subif)#ip rip authentication key-chain ORA
Router1(config-subif)#ip rip authentication mode md5
Router1(config-subif)#end
Router1#

Discussion

RIP authentication is one of the protocol enhancements that appeared in Version 2. It is not available for Version 1.

The first configuration example in this recipe uses plain-text authentication. In general, we recommend using the MD5 authentication because the plain-text version is far too easy to break. ...