The simplest and the most widespread classful distance vector routing protocol is the
Routing Information Protocol (version 1). RIP uses hop count as its metric for path selection.
Hop counts greater than 15 are marked as unreachable and broadcast messages every 30 seconds.
RIP being classful does not send subnet mask in its update. Default administrative distance is 120.
RIP Version 1 does not support classless (discontiguous) networks or VLSM instead RIP Version 2
support these
To enter router configuration mode
R1(config)#  router rip

To enable rip routing for a network
R1(config-router)# network directly_connected_classfull_network_address
EG:  R1(config-router)# network
         R1(config-router)# network

To check your RIP protocol configuration
R1(config)#  show ip route
R1(config)#  show ip protocols

To debug RIP protocol in a router
R1(config)# debug ip rip