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The purpose of IP multicast filtering is to optimize a switched network’s
performance, so multicast packets will only be forwarded to those ports
containing multicast group hosts or multicast routers/s witches, instead of
flooding traffic to all ports in the subnet (VLAN).
Configuring IGMP Parameters
You can configure the switch to forward multicast traffic intelligently.
Based on the IGMP query and report messages, the switch forwards traffic
only to the ports that request multicast traffic. This prevents the switch
from broadcasting the traffic to all ports and possibly disrupting network
performance.
Command Usage
•IGMP Snooping – This switch can passively snoop on IGMP Query
and Report packets transferred between IP multicast routers/switches
and IP multicast host groups to identify the IP multicast group
members. It simply monitors the IGMP packets passing through it,
picks out the group registration information, and configures multicast
filters accordingly.
•IGMP Query – A router, or multicast-enabled switch, can
periodically ask their hosts if they want to receive multicast traffic. If
there is more than one router/switch on the LAN perfo rming IP
multicasting, one of these devices is elected “querier” and assumes the
role of querying the LAN for group members. It then propagates the
service requests on to any adjacent multicast switch/router to ensure
that it will continue to receive the multicast service.
Note: Multicast routers use this information, along with a multicast
routing protocol such as DVMRP, to support IP multi casting
across the Internet.