Multicast on specific VLAN's /ports only!!

Unanswered Question
Sep 15th, 2008

Anyone know how to enable Multicast on specific VLAN's only. I have a 4507 switch which is trunked to a 7206 router where different VLAN's are supported through it(VLAN's are separated at the router using VRF's / dot1Q). I'm trying to figure out how to enable and allow specific VLAN's on the switch for Multicast. Is there a way to enable Multicast for specific VLAN's only???

I have this problem too.
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Giuseppe Larosa Mon, 09/15/2008 - 09:41

Hello Henry,

yes the command syntax allows this.

in global-config:

ip multicast-routing

then on each SVI vlan that should run multicast you do

int vlan X

ip pim sparse-dense-mode

if the L3 in on the c7206

ip multicast-routing

int g0/0.X

ip pim sparse-dense-mode

vlans were the command is not inserted will not be part of the multicast routing topology.

on the switches you need to enable IGMP snooping so that multicast forwarding is optimized within the ports of multicast-enabled vlans.

Be aware that if multicast is needed in a vlan and confined in that vlan the igmp snooping could cause problems if the multicast routing is not enabled for the same vlan (absence of a router acting as an IGMP querier for multicast groups receivers).

Hope to help

Giuseppe

hks10 Tue, 09/16/2008 - 10:27

Thanks for the info. I will give this a try.

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