Configuring Rip; Icmp Host Unreachable Message For Undeliverable Arps; Rip Parameters And Defaults; Rip Global Parameters - Foundry Networks Switch and Router Installation And Configuration Manual

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 Foundry Layer 3 Switch and the destination network.
A Foundry Layer 3 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 Foundry Layer 3 Switch receives a RIP update from another router that contains a path with fewer hops than
the path stored in the Foundry Layer 3 Switch's route table, the Layer 3 Switch replaces the older route with the
newer one. The Layer 3 Switch then includes the new path in the updates it sends to other RIP routers, including
Foundry Layer 3 Switches.
RIP routers, including the Foundry Layer 3 Switch, 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.
Foundry Layer 3 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 router 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 (router knows of no route to the destination address), the router 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 16.1 lists the global RIP parameters and their default values, and indicates where you can find configuration
information.
December 2000
Chapter 16

Configuring RIP

16 - 1