[nsp] multicast loop?

From: dec2 (dec2@inetu.net)
Date: Thu Dec 27 2001 - 10:35:39 EST


Greets.

We have a pair of 7206VXRs and a Cat 6509. The routers are connected with
a port-channel (2 x 100Mbit FEs) and again each router is connected to the
6509 with another port-channel (2 x 100Mbit FEs).

We run into a problem looking very much like a broadcast storm that sends
the 6509 into a fit -- it sporadicly forwards traffic during the storm.
It remains in a semifunctional state until it recieves a 'reset 3'.
Module 3 is a 48 port 100Mbit ethernet card and is currently the only
module to which we have devices connected.

The various stats we collect tell us that:

  1. There is a multicast storm of several million packets per second

  2. This storm appears to loop from Cat to router to router to Cat, etc.

  3. The storm persists until I reset the module.

  4. This traffic never makes it to my span ports -- The Cat discards
them.

The only suspicious activity which I've been able to match up with each
occurence of this outage is an IGMP multicast from a server on our network
to 224.0.0.2.

So I guess what I'm getting at here.... :) Any similar problems? Is
there something obvious that I'm overlooking which may lead to this kind
of activity? If I have a loop, I'm not seeing it. Anything I should look
for?

Any pointers appreciated. TIA.



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