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Cisco IOS Cookbook, 2nd Edition by Ian Brown, Kevin Dooley

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Adjusting Timers

Problem

You wish to tune your routing protocol performance to improve the time that the network takes to converge after a topology change.

Solution

RIP has several timers that control things like how often it sends updates and how long it takes to remove a bad route. You can adjust these values with the timers basic configuration command:

Router2#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router2(config)#router rip 
Router2(config-router)#timers basic 20 80 80 120  
Router2(config-router)#exit
Router2(config)#end
Router2#

Discussion

The timers basic command controls all of the adjustable timers for RIP:

Router2(config-router)#timers basic 20 80 80 120  

The four arguments are, in order, the update period, the invalid route timer, the holddown timer, and the flush timer. All of these times are in seconds.

The update period controls how often the router sends updates to its neighbors. The default update period is 30 seconds. Reducing this period can help improve convergence times. However, you have to remember that RIP sends the entire routing table in each update cycle. So if the routing table is large, reducing this period too much can cause serious bandwidth loading problems on slower links.

The invalid route timer controls how long the router will wait before a particular route is declared invalid. If the route disappears from routing updates from neighboring routers for this length of time, the router will mark it invalid. The router ...

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