IPv4 - RIP

Applies To: Windows Server 2008

In dynamic IP routing environments, IP routing information is propagated by using IP routing protocols. The Routing Information Protocol (RIP) is designed for exchanging routing information within a small to medium-size network.

The biggest advantage of RIP is that it is extremely simple to configure and deploy. The biggest disadvantage of RIP is its inability to scale to large or very large networks. The maximum hop count used by RIP routers is 15. Networks that are 16 hops or more away are considered unreachable. As networks grow larger in size, the periodic announcements by each RIP router can cause excessive traffic. Another disadvantage of RIP is its high recovery time. When the network topology changes, it may take several minutes before the RIP routers reconfigure themselves to the new network topology. While the work reconfigures itself, routing loops may form that result in lost or undeliverable data.

Initially, the routing table for each router includes only the networks that are physically connected. A RIP router periodically sends announcements that contain its routing table entries to inform other local RIP routers of the networks it can reach. RIP version 1 uses IP broadcast packets for its announcements. RIP version 2 uses multicast or broadcast packets for its announcements.

RIP routers can also communicate routing information through triggered updates. Triggered updates occur when the network topology changes and updated routing information is sent that reflects those changes. With triggered updates, the update is sent immediately rather than waiting for the next periodic announcement. For example, when a router detects a link or router failure, it updates its own routing table and sends updated routes. Each router that receives the triggered update modifies its own routing table and propagates the change.

Routing and Remote Access supports RIP versions 1 and 2. RIP version 2 supports multicast announcements, simple password authentication, and more flexibility in subnetted and Classless InterDomain Routing (CIDR) environments.

The Windows Server® 2008 implementation of RIP has the following features:

• Selection of which RIP version to run on each interface for incoming and outgoing packets.

• Split-horizon, poison-reverse, and triggered-update algorithms that are used to avoid routing loops and speed recovery of the network when topology changes occur.

• Route filters for choosing which networks to announce or accept.

• Peer filters for choosing which router's announcements are accepted.

• Configurable announcement and route aging timers.

• Simple password authentication support.

• The ability to disable subnet summarization.