Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

The routing table is established after RIP sends out one or more broadcast signals to all adjacent nodes in a network. Hop counts of these signals are tracked and entered into the routing table, which defines where nodes in the network are located.

The information that is used to update the routing table is sent as either a request or response message. In RIPv1, automatic updates to the routing table are performed as either one-time requests or periodic responses (every 30 seconds). RIP transports its responses or requests by means of user datagram protocol (UDP) over port 520.

RIP must receive regular routing updates to maintain a correct routing table. Response messages containing a router’s full routing table are transmitted every 30 seconds. If a router does not send an update within a certain amount of time, the hop count to that route is changed to unreachable (a route hop metric of 16 hops). Another timer sets the amount of time before the unreachable routes are removed from the routing table.

This first RIP version does not support variable length subnet mask (VLSM) or classless inter-domain routing (CIDR) and is not widely used.