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New Member

Layer 2 multicasting

I have a server that is multicasting images to workstations. I am trying to limit the multicast to only go to certain ports on a 4500 running IOS. I understand that I can turn on igmp snooping and because it has ASIC's it should work. However, the multicast originates in the same broadcast domain as the destination, so there are no routers or PIM enabled devices that the multicast flows through. Will igmp make a difference in this scenerio?

Cisco Employee

Re: Layer 2 multicasting

Hi Friend,

Can you confirm if you have any layer 3 interface configured on your 4500 switch for the vlan on which your multicast server and clients are connected? If yes then IGMP snooping will work.

IGMP snooping is not really supported on any Catalyst platform without an mrouter. The mechanism "breaks down" in the absence of an mrouter port. If you want a fix for this solution, you must have the switches somehow learn or know of an mrouter port.

Have a look at this link



New Member

Re: Layer 2 multicasting

Actually, I do have some layer 3 interfaces on the switch. One is just a layer 3 vlan interface. That interface has the IP address of the LAN and serves as the gateway address. Do I need to configure the vlan interface as a mrouter port? If so, how. I still don't want any multicasting routed outside of the LAN.

New Member

Re: Layer 2 multicasting


To use IGMP you must have an IGMP querier.

Normally an IGMP querier would be a router, but some switches with the newer versions of IOS support an IGMP querier function.

Read this: