duplicate multicast on a bridge

Unanswered Question
Feb 9th, 2009

Hi, I have a situation with a router connected to 2 switches on the same LAN that are bridged together. The BVI has pim dense-mode and there is a tunnel to another network. The problem is that all incoming multicast traffic from the LAN is sent twice over the tunnel (I presume from debugging that it is because the packets are coming in through both interfaces that are bridged together. The router is a 2811. Any insight on this would be great, thanks.

I have this problem too.
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owillins Fri, 02/13/2009 - 13:17

Duplicate multicast packets are symptoms of several things:

- An Ethernet-level device (e.g. bridge) that doesn't understand multicast so reforwards it. This is easy to track to the right subnet using mtrace's packet statistics, but hard to track to the final device because it doesn't change the ethernet source address.

- Forwarding loops. This is often due to a misconfigured router


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