Stop multicast from flooding all ports

Unanswered Question
Oct 5th, 2008

Is it possible to stop multicast traffic from flooding all switch ports on a VLAN without a router interface on it? IGMP snooping only seems to work if there is a router interface present on the network with PIM enabled.

I believe I can statically assign the switch ports for the multicast traffic, but I need a way to have this happen dynamically.



I have this problem too.
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Jon Marshall Mon, 10/06/2008 - 01:59


Yes it is but it depends on which switch you are using. For IGMP snooping to work then something else needs to make the IGMP queries. This as you say is usually done when multicast routing is enabled on L3 interface. However most switches support the IGMP snooping querier function which will make the IGMP queries without haviing to enable PIM on a L3 interface.

Have a search on Cisco site for configuration docs for your switch and see if the IGMP snooping querier function is supported.


vaniello Mon, 10/06/2008 - 08:07

I am using a 4948 switch running IOS v12.2(31)SGA. The "ip igmp snooping querier" command doesn't seem to be available on the switch.

What other options do I have?


Jon Marshall Mon, 10/06/2008 - 08:16

Unfortunately i don't believe the 4500 or 4900 switches support this function.

If you want your switch to learn these dynamically and you cannot use IGMP snooping querier then the only other option you have is to enable multicast-routing and configure PIM on the releavant vlan interface.

Other than that it is just static mappings i'm afraid.



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