Cisco IOS Cookbook, 2nd Edition

Enabling Nonperiodic Updates

Problem

You want to reduce RIP bandwidth requirements by configuring routers to forward changes only to the routing table instead of forwarding the entire routing table every 30 seconds.

Solution

The ip rip triggered interface configuration command tells the router to only send those parts of the RIP database that have changed, instead of sending the entire database on each RIP update cycle:

Router1#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router1(config)#interface Serial0/0.2
Router1(config-subif)#ip rip triggered
Router1(config-subif)#end
Router1#

Be sure to enable these nonperiodic “triggered” updates on the adjacent router as well:

Router2#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router2(config)#interface Serial0.1
Router2(config-subif)#ip rip triggered
Router2(config-subif)#end
Router2#

Tip

You must enable this feature on both routers sharing the point-to-point link, or you risk losing all routing information.

Discussion

It is important to distinguish between this feature and the triggered updates that are part of the standard RIP protocol. What is normally called a triggered update in RIP simply means that the protocol sends out updated route information as soon as it notices a change, rather than waiting for the next update cycle. The triggered update feature in this recipe would be more accurately called a nonperiodic update; it simply means that the router generally refrains ...