From: David FAHED (dfahed@xxxxxxxxxxxx)
Date: Mon Oct 16 2000 - 11:49:29 GMT-3
A good reference is : Routing TCP/IP (Jeff Doyle) page 193-196.
- Update timers : timer for periodic update (default 30s) + RIP_JITTER (random
to
prevent colision - 15% of the update timers)
- Invalidation timer: use to limit the amount of time a route can stay in routi
ng table
without being update (default 180s) - Start at the last update of the route.
- Flush timer: is set to 240s - 60 second longer than the Invalid timer. The ro
ute will
be advertised with unreachable metric (at the end of the Invalidation Timer) un
til the
flush timer expires (during this 60 s the route is possibly down in the routing
table),
at which time the route is removed from the routing table. Start (like invalida
tion
timer) at the last update of the route.
- Holddown timer: an update with a hop count higher than the metric recorded in
the
routing table will cause the route to go into holddown for 180 s (by default).
Hop this will give you some help.
Yours David.
Guoxing Jiang wrote:
> Hello
>
> Before today I think I know the rip timers very clearly, but I am so puzzled
> now after I did some practice. The default timers for rip is 30 180 180 240.
> I think the flush timers just start at the same time as holddown timer. But
> in practice, I found that isn't true, I remove one network from rip network,
> after 180 sec, the route in routing table became possibly down and the holddo
wn
> timers was really started, I thought the flush timers should started at this
time
> too. But just after 60 sec, the route was flushed from the routing
> table. It seems the flush timers started for the last update time. I want to
find
> some things useful in the CCO. But I am more puzzled, they say the
> flush timers should set more than holddown timers(that's very true), but they
don't
> say when the flush timers start( but in many books the authors say the flush
> timers start at the same time as holddnow timers and I think it is reasonable
).
> and there is a example after explaining the command in the CCO. The timers is
> 5 15 15 30. 30 = 15 + 15. they explain that the route will became possibly do
nw
> after 15 sec and after another 15 sec holddown, the route will be flushed.
> Maybe I can think the flush timer should no more than the sum of
> invalid and holddow timer. why they don't set the default timers to
> 30 180 180 360. when do the flush timers start at all? from the last update
> or just from the time when the route becam possibly down.
>
> one more thing, if I shutdown one interface. the route became possibly down s
oon.
> I using "show ip route *.*.*.* " check the info about the timer. I saw the
> last update timers is auto added by 180 sec, and after another 60 sec, the ro
ute
> was flushed. That really accelerate the convergence. but it let me more puzzl
ed.
>
> can you explain clearly to me?
>
> thanks.
>
> jiang
> --
> Best regards,
> Guoxing Jiang mailto:jianggx@transcentury.com.cn
>
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