By default, RIP advertises all RIP routes to each peer every 30 seconds. RIP uses a hop count metric to determine the distance between the packet’s source and destination. The metric/cost values for a valid route is 1 through 15. A metric value of 16 (infinity) indicates that the route is no longer valid and should be removed from the router’s routing table.
Each router along the path increments the hop count value by 1. When a router receives a routing update with new or different destination information, the metric increments by one.
The maximum number of hops in a path is 15. If a router receives a routing update with a metric of 15 and contains a new or modified entry, increasing the metric value by one will cause the metric increment to 16 (infinity). Then, the destination is considered unreachable.
The router implementation of RIP uses split horizon with poison reverse to protect from such problems as ‟counting to infinity”. Split horizon with poison reverse means that routes learned from a neighbor through a specified interface are advertised in updates out of the same interface but with a metric of 16 (infinity).