What Is the Routing Information Protocol?

The Routing Information Protocol (RIP) is a routing protocol based on the distance vector algorithm. It uses the number of hops as a measurement standard.

Chinese name: Routing Information Protocol
Foreign name: Routing Information Protocol

Features: Use hop counts as a measure
Category: Dynamic routing protocol

Introduction to Routing Information Protocol

The Routing Information Protocol (RIP) is a routing protocol based on the distance vector algorithm. It uses the number of hops as a measurement standard. It has lower requirements in terms of bandwidth, configuration, and management, and is mainly suitable for smaller networks.

Routing Information Protocol Version

Version: RIPv1, RIPv2, and RIPng, the former two are used for IPv4, and RIPng is used for IPv6.

Among them, RIPv1 is a classful routing protocol that does not support VLSM and CIDR; sends messages in the form of broadcast; does not support authentication. RIPv2 is a classless routing protocol that supports VLSM, routing aggregation and CIDR; supports sending messages in broadcast or multicast (224.0.0.9); supports plain text authentication and MD5 cipher text authentication.

History of routing information protocols

Both Xerox and the University of California, Berkeley developed early versions of RIP in the early 1980s.

RFC 1058 of 1988 explained the RIP protocol, which was later called RIPv1.

In 1998, the IETF launched an improved version of the RIP standard RFC 2453, namely RIPv2: Supports subnet mask information; supports routing object flags; supports routing update authentication.

In 1997, the IETF introduced the next-generation RIP protocol, RIPng's proposed standard RFC 2080.

How routing protocol works

(1) Route establishment

After the router runs RIP, it will first send a route update request, and the router receiving the request will send its own RIP route to respond; after the network is stable, the router will send routing update information periodically.

(2) Calculation of distance vector

The unit of RIP measurement is the number of hops, and its unit is 1, which means that the cost of each link is set to 1, regardless of the actual bandwidth and delay of the link. RIP allows up to 15 hops.

RIP uses metrics to indicate the distance between it and all known destinations.

When a RIP update packet arrives, the receiving router compares each entry in its own RIP routing table and corrects its own RIP routing table according to the distance vector routing algorithm.

(3) Timer

Periodic update timer: It is used to stimulate the update of the routing table of the RIP router. Each RIP node has only one update timer, which is set to 30s. Every 30s the router broadcasts its own routing table information to its neighbors. The timer of each RIP router is independent of other routers in the network, so they are unlikely to broadcast at the same time.

Timeout timer: used to determine whether a route is available. Each route has a timeout timer set to 180s. When a route is activated or updated, the timer is initialized. If no update is received for that route within 180s, the route is invalidated.

Clear timer: used to determine whether to clear a route. Each route has a clear timer, which is set to 120s. When the router realizes that a route is invalid, it initializes a clear timer. If it has not received the update of this route within 120s, it deletes the route from the routing table.

Delay timer: A random delay timer set to avoid broadcast storms triggered by updates, with a delay time of 1 to 5 seconds.

(4) Loop

When the network fails, a routing loop may occur in the RIP network. You can avoid loops by split horizon, poison reverse, trigger update, and suppression time.