Verifying Propagation of all the networks on all the Routers
R1#show ip route
R2#show ip route
R3#show ip route
As it is clear that all the routers have all the networks and their respective routes present in their routing table. In R1’s routing table, it has the route to loopback address 1.1.1.1 of R3 via 10.1.1.2 present at R2’s interface. This route shows the AD value of 120 that is RIP specific and a metric of 2 which means the frame needs to cross two networks or two routers in order to reach the network, i.e., R2 and R3 in this case. Now, we will be applying the offset-list to this route to increase its metric.
Note: Here we are using RIP version 1, therefore the routes advertised are classful and thus the subnet mask present in the routing table is /8 (because the IP address/network belongs to class A of IP addresses).
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.