Configuring RIP on all Routers
On R1:
R1(config)#router rip R1(config-router)#network 10.1.1.0 R1(config-router)#exit
On R2:
R2(config)#router rip R2(config-router)#network 10.1.1.0 R2(config-router)#network 20.1.1.0 R2(config-router)#exit
On R3:
R3(config)#router rip R3(config-router)#network 20.1.1.0 R3(config-router)#network 1.1.1.1 R3(config-router)#exit
Configuring RIP Route Metric Offset-Lists in Cisco
RIP stands for Routing Information Protocol which is a Distance Vector Routing Protocol (one of the types of Dynamic Routing Protocol). It is a DVRP that relies on the hop count as its metric to calculate the best path to the destination. It uses UDP (User Datagram Protocol) as its Transport Layer Protocol with port 520.
A metric is a value assigned to an IP route that generally tells the path cost of reaching that particular network through a particular interface. It can be calculated in terms of link speed, hop counts, or time delay.
RIP uses hop counts as its metric value, i.e., the number of networks or routers the frame has to cross in order to reach the destination network. RIP allows a range of metrics from 1 to 16, where the last legitimate and accepted value is 15 (max value of metric in RIP). It uses 16 as a metric value to advertising the routes that are no longer available in the router’s routing table and are inaccessible (infinite path cost). This process of advertising routes having a metric value of 16 is also known as Route Poisoning.