RIP Timers

Hi,

I'm trying to fully understand the timers used in RIP.

Update timer: Send updates every 30 seconds
Invalid timer: After 180 seconds invalidate routes but keep them in routing
table
Hold down timer: 240 seconds, should be used when we receive route with
higher metric than in routing table?
Flush timer: After 240 seconds delete route from routing table

I did a very basic lab with three routers and debugging enabled (ip routing,
rip database and rip events) and tried to look at the output.

*Mar 1 00:13:46.595: RIP-DB: invalidated route of 1.1.1.1/32 via
192.168.0.2
*Mar 1 00:13:46.595: RIP-DB: Remove 1.1.1.1/32, (metric 4294967295) via
192.168.0.2, FastEthernet0/0

This is after roughly 180 seconds, this must be the invalid timer in action.
Is there a reason why the metric is so high, it seems to be 2^32. Also I'm
not seeing that the updates sent out are sent with a metric of 16, shouldn't
that be the case?

I'm not sure how to see the hold down timer in action, is there a good test
to run?

After 240 seconds the garbage collector flushes the routes:

*Mar 1 00:14:46.603: RIP-DB: garbage collect 1.0.0.0/8
*Mar 1 00:14:46.603: RIP-DB: garbage collect 1.1.1.1/32

Can anyone please shed some light on these timers. Thanks.

Daniel
http://www.lostintransit.se

Blogs and organic groups at http://www.ccie.net
Received on Thu Mar 31 2011 - 09:04:23 ART