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Enable multicast in switching network

I am trying to enable multicast on my L2 network attached scenario.

Is "ip igmp snooping" only command on all of my L2 switches that i needed?

  • WAN Routing and Switching
1 REPLY
Cisco Employee

Re: Enable multicast in switching network

Hello,

For a plain L2 multicast, you do not need to activate the IGMP Snooping feature at all. The multicast will be L2-flooded to all stations but only those stations that subscribed to the particular multicast group will process the frames. Also note, however, that the IGMP Snooping is activated by default on all Catalyst switches and it is not necesary to activate it explicitly.

If you do activate the IGMP Snooping in your particular topology then you must also activate the IGMP Querier function on your switch. The reason is that for the IGMP Snooping to work, the IGMP Membership Report messages must be continuously received by the switch. However, these messages are only sent from stations when initially subscribing to a multicast group, and later only as a response to a IGMP Membership Query message. These Membership Query messages are usually sent by multicast routers but you do not have any in your network. Therefore, your switch must be made responsible for originating these queries.

Assuming that the ports on your switch are placed into VLAN 1 and the IP network you're using is 10.0.1.0/24, these configuration commands should be added to your configuration:

interface Vlan 1

  ip address 10.0.1.254 255.255.255.0

  no shutdown

ip igmp snooping querier

This should make it work

Best regards,

Peter

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