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Prevent 3560 port from becoming mrouter port



I am trying to enable IGMP snooping on a 3560, which is located between a 4924 and 4500, both of which are configured with "ip pim sparse-mode" on the interfaces that face each other, and belong to the same VLAN.  Multicast traffic is streaming from a port connected to the 4924 in the direction of the 4500, but I need to have the 3560 open or close the port to the 4924 for select groups - hence IGMP snooping.

The 4500 is currently configured with "ip igmp helper-address <address_of_4924>", as it needs to forward the IGMP join/leave requests from the Set-Top Boxes that are connected to it towards the 4924, in order to trigger the opening/closing of ports on the 3560.

The issue that I am currently seeing is that the 3560 is detecting both ports - the port to the 4924 and the port to the 4500 - as mrouter ports, and hence it is not stopping the flow of multicast traffic towards the 4500, even when there are no receivers.

REX#sh ip igmp snooping mrouter

Vlan    ports

----    -----

  70    Gi0/1(dynamic), Gi0/48(dynamic)

In order to prevent the 3560 forwarding the m/cast traffic to the 4500 when there are no receivers present, I need to prevent Gi0/1 from being detected as a mrouter port.  Are there any commands that I can use to do this?  What about ACLs?  I have tried denying "igmp any any host-query" inbound on the 3560, and/or outbound on the 4500, but this doesn't seem to work.




Have you looked into PIM snooping on the 3560... I know its been over two months since you posted this but I have been researching a few multicast knobs and came across this exact same scenario.... PIM snooping is supposed to prevent the switch from flooding multicast to the mrouter port... You may have discovered this possibility already too...

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