RIP - Routing and metric incrementing

In a network topology using RIP (Routing Information Protocol), when a router loses connectivity to a directly connected network, it may still receive updates about that network from neighboring routers. For example, refer to the following diagram:

If R3 loses connectivity to the 3.3.3.0/24 network, R2 may still advertise a route to 3.3.3.0/24 with a hop count of 1. Upon receiving this update, R3 will add 1 to the metric, resulting in a hop count of 2 for the route to that destination via R2.

This process of incrementing the metric by 1 for each hop is a standard behavior in RIP to account for the additional distance to the destination. However, in certain topologies, this can lead to issues where routers continuously advertise routes to a network they cannot actually reach. This results in the metric increasing with each update until it reaches 15, which RIP considers as infinite, rendering the network unreachable.

Understanding this behavior is crucial for diagnosing and resolving routing issues in RIP-based networks.

Links:

https://forum.networklessons.com/t/rip-distance-vector-routing-protocol/876/72?u=lagapidis

https://networklessons.com/rip/rip-distance-vector-routing-protocol/