[c-nsp] 6500 IGMP snooping database now bound to MAC address and not switchport?

Phil Mayers p.mayers at imperial.ac.uk
Wed Feb 9 12:51:50 EST 2011

On 09/02/11 16:57, Sam Stickland wrote:
> All,
> I encountered some strange, but beneficial, behaviour in the lab. We
> connected a server with teamed NICs to two 6500s running SXH2a. The
> NIC teaming is active/standby using only a single MAC and IP address.
> The server joins a multicast group and starts receiving traffic. We
> found that if we pull the primary NIC everything, including the
> multicast traffic, fails over to the standby NIC, losing a couple of
> packets at most.
> The strange thing is that packet captures don't show the server
> re-issuing the IGMP join or sending any membership reports on the
> standby NIC. In the past this would had resulted in a loss of
> multicast traffic until the IGMP state is rebuilt on the new switch
> port. But no longer.

Interesting. Have you tried monitoring a "debug ip igmp" and friends 
whilst this happens?

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