Multicast Filtering 29
Figure 7   The effect of multicast filtering
Multicast Filtering
and Your Switch
Your Switch provides automatic multicast filtering support using IGMP 
(Internet Group Management Protocol) Snooping. It also supports IGMP 
query mode.
Snooping Mode 
Snooping Mode allows your Switch to forward multicast packets only to 
the appropriate ports. The Switch “snoops” on exchanges between 
endstations and an IGMP device, typically a router, to find out the ports 
that wish to join a multicast group and then sets its filters accordingly
Query Mode
Query mode allows the Switch to function as the Querier if it has the 
lowest IP address in the subnetwork to which it belongs.
IGMP querying is disabled by default on the Switch 3812 and 
Switch 3824. This helps prevent interoperability issues with core products 
that may not follow the lowest IP address election method.
You can enable or disable IGMP query mode for the Switch using the 
Bridge > Multicast filter > IGMP > Querymode operation on the Web 
Interface.