IGMP Snooping

Hi Sims,

The router is there since normally hosts use IGMP to indicate that they are interested in receiving a certain multicast group. Routers listen to these messages and forward multicast traffic is required.

If the switch doesn’t have a routed port then it will drop all incoming IGMP membership reports from hosts. If you don’t want this, then you should disable IGMP snooping.

There is once exception though. (Routing) protocols that use the 224.0.0.x range also don’t use IGMP when they want to receive multicast traffic. Examples are protocols like RIP, EIGRP, HSPR, etc. They all use MAC address 0100.5e00.00xx which is ignored by IGMP snooping.

Traffic that uses 224.0.0.x (0100.5e00.00xx) as the destination is always flooded by the switch.

Hope this helps.