[c-nsp] igmp snooping inside 802.1q trunks

[lee.e.rian at census.gov]

Vladimir Ivashchenko <hazard at francoudi.com> wrote on 01/30/2006 01:50:58
PM:

> Hi List,
>
> I have a problem with multicast on 802.1q trunk ports. We have a network
> consisting of Catalyst 3560 with multicast source + a number of Catalyst
> 6500 where receivers are placed. Multicast is flat on a single VLAN (no
> routers) and IGMP snooping is configured on all the switches.
>
> The problem is that 6500 seems to unconditionally forward all multicast
> traffic to all trunk ports even if there are no receivers there. E.g.
> "show mac-address-table multicast" does not show any entries for that
> port, however it still receives all multicast traffic.
>
> Any ideas?

The 6500 is going to forward multicast traffic to any routers it learns
about.
Does a "show multicast router" on the 6500 list all the trunk ports?

Lee