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

[Sam Stickland]

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.

My guess is that the IGMP snooping mechanism is now recording the MAC address of the reporter and updating the snooping tables when the MAC address moves.

But I can't find this documented anywhere, so I'd hate to rely on this behaviour.

Has anyone else heard of this?

Regards,

Sam