> It's not true. The destination MAC address is the multicast L2 MAC. > > > capture seems to be suggesting)? If this is true, then what > is the process > > that gets the stream to the router, i.e. how does the > switch determine that > > it should add the corresponding multicast MAC to the port > facing the router? > > The "router port" bit of IGMP snooping. Broadly speaking, when the > switch sees IGMP queries coming in on a port, it marks that port as a > router port and floods all multicast traffic up it. > Thanks for the info.; the ethereal capture seemed to be indicating this, but as we are having a problem at the moment, I wanted to be sure that this was normal behaviour. So now a question regarding our issue, has anyone seen anything similar to the following? We have a core of 6500s running sup720s with native IOS version 12.2(18)SXD4. When a server sources a multicast stream (we have seen this on 2 of our 6500s so far), captures show that the stream corrective passes through the cisco WS-C2970G-24TS-E switch towards the 6500, but as soon as it enters the 6500 (this 6500 can be the server's gateway or just passing the traffic at layer 2 to another 6500), all ports that are a member of the same VLAN as the server receive the traffic, almost as if IGMP snooping is turned off or broken. I have shown that IGMP snooping is enabled using the slightly convoluted command (as per Cisco docs) "sh ip igmp int vlan 404 | inc global". The command gives
"IGMP snooping is globally enabled" Has anyone else seen this and know how to fix it (maybe time for a software upgrade)? Michael Robson. _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
