RIP is an interior gateway protocol (IGP) that uses a distance-vector (Bellman-Ford) algorithm to determine the best route to a destination. The algorithm advertises network reachability by advertising prefix/mask and the metric (also known as hop count or cost). RIP selects the route with the lowest metric as the best route. In order for the protocol to provide complete information about routing, every router in the domain must participate in the protocol.
RIP is a routing protocol based on a distance vector (Bellman-Ford) algorithm, which advertises network reachability by advertising prefix/mask and the metric (also known as hop count or cost). RIP selects the route with the lowest metric as the best route. RIP differs from link-state database protocols, such as OSPF and IS-IS, in that RIP advertises reachability information directly and link-state-database-based protocols advertise topology information. Each node is responsible for calculating the reachability information from the topology.
The router software supports RIPv1 and RIPv2. RIPv1, specified in RFC 1058, was written and implemented before the introduction of classless interdomain routing (CIDR). It assumes the netmask information for non-local routes, based on the class the route belongs to:
class A
8 bit mask
class B
16 bit mask
class C
24 bit mask
RIPv2 was written after CIDR was developed and transmits netmask information with every route. Because of the support for CIDR routes and other enhancements in RIPv2 such as triggered updates, multicast advertisements, and authentication, most production networks use RIPv2. However, some older systems (hosts and routers) only support RIPv1, especially when RIP is used simply to advertise default routing information.
RIP is supported on all IP interfaces, including both network and access interfaces.