RIP Facts

RIP FactsThe Routing Information Protocol (RIP) is a simple, effective routing protocol for small- to medium-sized networks. Be aware of the following facts about RIP:

• RIP is a distance vector routing protocol.
• RIP uses split horizon with poison reverse to prevent routing loops.
• RIP shares its entire routing table at each update interval (except for routes that are not being advertised to prevent routing loops).
• By default, routing updates are sent every 30 seconds. The invalid timer default is 180, the holddown timer default is 180, and the flush timer default is 240.
• RIP uses the hop count as the routing metric. The hop count is the number of routers between the source network and the destination network.
• RIP has a maximum of 15 hops from the source to the destination network. An unreachable network (or a network that is no longer available) is indicated by a hop count of 16.
• There are two versions of RIP: RIP (version 1), and RIP version 2.
  • RIP (version 1) uses broadcasts to send routing updates. RIPv2 uses multicasts sent to the multicast address 224.0.0.9.
  • RIP (version 1) uses only classful routing, so it uses full address classes, not subnets. Autosummarization with RIP happens on default class boundaries. RIPv2 supports VLSM, sends subnet masks in the routing update, and supports manual route summarization.
• RIP can maintain up to six multiple paths to each network, but only if the cost is the same. It supports load balancing over same-cost paths. The default is support for up to four equal-cost routes.

Note: Because RIP uses the hop count in determining the best route to a remote network, it might end up selecting a less than optimal route. For example, suppose that two routes exist between two networks. One route uses a 56 Kbps link with a single hop, while the other route uses a Gigabit link that has two hops. Because the first route has fewer hops, RIP will select this route as the optimal route.