IPv4 Multicast

Wed May 19 00:44:34 UTC 2010

>>I can see that IGMP is enabled on all interfaces but do I need enable something else?

You need to have a multicast router or enable IGMP querier on one of your switches.  For IGMP snooping to work something on the network has to be sending out PIM hellos or IGMP query messages.  Without that the switch will flood multicast traffic to all ports

"The reason for this issue is that IGMP snooping is not really supported on any Catalyst platform without an mrouter."
http://www.cisco.com/en/US/products/hw/switches/ps708/products_tech_note09186a008059a9df.shtml#understand

Note if you go the router method ALL multicast traffic will be sent to the router, so don't expect it to work if you have 5Gbps of multicast connected to a router with a 1Gbps interface.

If all your multicast traffic is on the same layer2 network then the IGMP querier feature should work fine.

-Tony