>Cisco routers default to update every 'so often' where as the 3com routers
>update when a change has been made...this is why the cisco routers drop all
>updates after so long because the 3com router is no longer sending them. On
>the cisco side you can change the update interval to match and all should be
>well.
>
>-Patrick
I'm not sure I understand what you mean by "update every so often."
You may be touching on a rather subtle issue in the design of routing
protocols, discovered by Sally Floyd.
Many RIP (and for that matter IGRP) implementations would reset their
update timer when they received new information, so that when the 30
second timer expired, they would send out the most accurate
information. Unfortunately, when this behavior extends over a large
number, it acts as a weak but real time synchronization mechanism,
causing all the 30 second timers to expire at about the same time,
causing periodic peak loads.
The answer is to put slight randomization into the "30 second" or
whatever periodic timer is used. Cisco, and most other vendors, do
jitter most of their periodic timers.
If 3Com stops sending periodic updates simply because there is no
change, that is a major violation of conformance to the RIP standard.
RIP and IGRP rely on periodic updates to detect router and link
failures.
>
>>>> "Provost, Robert" 07/26/01 04:34PM >>>
>> We have a Frame Relay network with 3Com and Cisco routers. The core
>> routers are 3Com PathBuilders S500 series. All routers are configured
>> for RIP version 2 (VLSM). All of the 3Com router's RIP routes show up
>> fine in the Pathbuilder's RIP table. The Cisco router's RIP routes
>> show up, then "garbage out"(show as unreachable), then show up again,
>> then "garbage out" , etc. Our current work around is to add static
>> routes to the Pathbuilders for all Cisco routers.
>>
>> Does anyone have any info on this issue?
>>
>> Any help is greatly appreciated.
>>
>> Thanks,
> > Robert Provost
Message Posted at:
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