IGRP (Internal Gateway Routing Protocol)


You can have both RIP and IGRP running at the same time.  IGRP is Cisco’s protocol that allows all routers within one AS (Autonomous System) to communicate. 


This is done the same way as RIP - to enable IGRP:


router IGRP AS#                      (we used AS=10 for each router in the domain)


            maximum-paths 4         (optional - limit multiple routes to the same subnet to 4)


NOTE1:  after the word “network”, you use the classful network boundary instead of the subnet address.  The router may have multiple /24 Class C address networks connected to it, but with RIP, you want to define the entire network, which is  -  do this for each router on the network