Multicast Filtering And Your Switch - 3Com 3824 Implementation Manual

Multicast Filtering 29
Figure 7 The effect of multicast filtering
Multicast Filtering Your Switch provides automatic multicast filtering support using IGMP
and Your Switch (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.