Cisco Systems 78-11741-02 Allowing Unicast Updates for RIP, Applying Offsets to Routing Metrics

Configuring Routing Information Protocol

RIP Configuration Task List

Allowing Unicast Updates for RIP

Because RIP is normally a broadcast protocol, in order for RIP routing updates to reach nonbroadcast networks, you must configure the Cisco IOS software to permit this exchange of routing information. To do so, use the following command in router configuration mode:

Command	Purpose
Router(config-router)# neighbor ip-address	Defines a neighboring router with which to exchange routing
	information.

To control the set of interfaces with which you want to exchange routing updates, you can disable the sending of routing updates on specified interfaces by configuring the passive-interfacerouter configuration command. See the discussion on filtering in the “Filter Routing Information” section in the “Configuring IP Routing Protocol-Independent Features” chapter.

Applying Offsets to Routing Metrics

An offset list is the mechanism for increasing incoming and outgoing metrics to routes learned via RIP. Optionally, you can limit the offset list with either an access list or an interface. To increase the value of routing metrics, use the following command in router configuration mode:

Command	Purpose
Router(config-router)# offset-list[access-list-number	Applies an offset to routing metrics.
access-list-name] {in out} offset [interface-type
interface-number]

Adjusting Timers

Routing protocols use several timers that determine such variables as the frequency of routing updates, the length of time before a route becomes invalid, and other parameters. You can adjust these timers to tune routing protocol performance to better suit your internetwork needs. You can make the following timer adjustments:

•The rate (time in seconds between updates) at which routing updates are sent

•The interval of time (in seconds) after which a route is declared invalid

•The interval (in seconds) during which routing information regarding better paths is suppressed

•The amount of time (in seconds) that must pass before a route is removed from the routing table

•The amount of time for which routing updates will be postponed

It also is possible to tune the IP routing support in the software to enable faster convergence of the various IP routing algorithms, and, hence, quicker fallback to redundant routers. The total effect is to minimize disruptions to end users of the network in situations where quick recovery is essential.

In addition, an address family can have explicitly specified timers that apply to that address-family (or VRF) only. The timers basic command must be specified for an address family or the system defaults for the timers basic command are used regardless of what is configured for RIP routing. The VRF does not inherit the timer values from the base RIP configuration. The VRF will always use the system default timers unless explicitly changed using the timers basic command.

Cisco IOS IP Configuration Guide

IPC-201