Verifying MD5 Authentication

Verifying MD5 Authentication

By configuring the Rtr1 and Rtr2 as shown, all routing update exchanges are authenticated before being accepted. Verify this by observing the output obtained from the debug ip rip command:

Rtr1#debug ip rip   
RIP: received packet with MD5 authentication
RIP: received v2 update from 192.168.2.2 on Serial0
     192.168.3.1/24 via 0.0.0.0 in 1 hops

MD5 authentication uses the one-way, MD5 hash algorithm in which the routing update doesn’t carry the actual password (key) for the purpose of authentication. A128-bit message, generated by running the MD5 algorithm on the password, and the message are sent along for authentication. The recipient device runs the same hash using the key information configured and, assuming it generates the same 128-bit message, the update will be accepted. MD5 hashing is covered in greater detail in Chapter 8.