[c-nsp] Multicast Behavior on a Cat issue...

[Dave Temkin]

Does anyone have a link to how multicast should behave on a Catalyst?

It's my understanding that when a host sends out traffic to a group it's
subscribed to, the Cat is smart enough to check the source MAC address of
the traffic and not forward the traffic back to the port that sent it into
the network.   I'm seeing an issue where this isn't happening - a host is
publishing a significant amount of multicast, and when we span the port we
see two copies of the traffic (from the host out to the switch, and then
from the switch back to the host).

Cisco hasn't been much help to us thus far, but we can't imagine this is
the intended behavior.

Thanks,
-Dave