Chapter 7

Configuring RIP

Routing Information Protocol (RIP) is an IP route exchange protocol that uses a distance vector (a number representing distance) to measure the cost of a given route. The cost is a distance vector because the cost often is equivalent to the number of router hops between the HP routing switch and the destination network.

An HP routing switch can receive multiple paths to a destination. The software evaluates the paths, selects the best path, and saves the path in the IP route table as the route to the destination. Typically, the best path is the path with the fewest hops. A hop is another router through which packets must travel to reach the destination. If the HP routing switch receives a RIP update from another router that contains a path with fewer hops than the path stored in the HP routing switch’s route table, the routing switch replaces the older route with the newer one. The routing switch then includes the new path in the updates it sends to other RIP routers, including HP routing switches.

RIP routers, including HP routing switches, also can modify a route’s cost, generally by adding to it, to bias the selection of a route for a given destination. In this case, the actual number of router hops may be the same, but the route has an administratively higher cost and is thus less likely to be used than other, lower-cost routes.

A RIP route can have a maximum cost of 15. Any destination with a higher cost is considered unreachable. Although limiting to larger networks, the low maximum hop count prevents endless loops in the network.

HP routing switches support the following RIP types:

•Version 1

•V1 compatible with V2

•Version 2 (the default)

ICMP Host Unreachable Message for Undeliverable ARPs

If the routing switch receives an ARP request packet that it is unable to deliver to the final destination because of the ARP timeout and no ARP response is received (routing switch knows of no route to the destination address), the routing switch sends an ICMP Host Unreachable message to the source.

RIP Parameters and Defaults

The following tables list the RIP parameters, their default values, and where to find configuration information.

RIP Global Parameters

Table 7.1 lists the global RIP parameters and their default values, and indicates where you can find configuration information.

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