CCNA - question about RIP timers

Author

question about RIP timers

worrywarm

2004-02-24, 12:56 pm

You are troubleshooting a network. In particular, you are concerned about how long 202.20.10.0 and 202.20.11.0 will be kept in the routing table. What's the max time for those routes would be kept in the routig table?
Router# sh ip route
Gateway of last resort is not set
R 202.20.10.0/24 is possibly down, routing via 202.30.9.1,serial 1
R 202.20.11.0/24 is possibly down, routing via 202.30.9.1,serial 1
...

a. 30s
b. 60s
c. 240s
d. 360s
e. 630s
answer: C

Is that because 240 is flush timer?? If it's IGRP, others are exactly same, then it would be 630s?? Flush timer should be start when the route become invalid, right? But is there any relationship between holderdown timer and invalid/flush timer?

(I ask a similar question before, nobody answers, now I'm still confused)

Anyone knows?
Thank you very much!

npo3po

2004-02-24, 2:22 pm

hey worry, firstoff the timers are simply series of points along a timeline that dictate to the router what actions to take with regards to a particular route once it reaches certain points along that timeline. Now different protocols have different timers(update, holddown, and flush), the route update timer for RIP is 30sec(that's for Ip ofcourse), holdtimer is 180sec, and flush is 240sec. For IGRP, update is 90secs, invalid is 270sec, holddown is 280sec, and flush is 630sec.

The route invalid timer, 180sec for RIP, is the amount of time that must elapse for a particular route to become marked invalid, because the router has simply not heard anything about that route, no updates.

The holddown timer has to do with the route becoming marked "unreachable" based on an update, that is also 180sec for RIP, the route is now suppresed, this is point where the router waits for any other updates that would give it a better metric for that route.

But once the router hits the 240sec mark the route is removed completely.

Hope that helps
Amir

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