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IGMP S
NOOPING
C
OMMANDS
33-5
ip igmp snooping leave-proxy
This command suppresses leave messages unless received from the last
member port in the group. Use the no form to restore the default.
Syntax
ip igmp snooping leave-proxy
no ip igmp snooping leave-proxy
Default Setting
Disabled
Command Mode
Global Configuration
Command Usage
• This command setting is only effective if IGMP snooping is enabled.
• Any port can be designated as a multicast router port through dynamic
or static configuration, including ports on Layer 2 or 3 switches. If
there is more than one multicast router on a LAN segment
performing IP multicasting, one of these devices is elected “querier”
and assumes the role of querying the local segment for group
members. It propagates service requests on to any upstream multicast
router to ensure that it will continue to receive the multicast service.
• Multicast router ports not serving as an IGMP querier also forward
group leave messages on to the local querier. When a non-querier port
receives an unsolicited leave message, it first checks whether this port
is the last dynamic member port in the group. If this is (1) not the last
member port, (2) not a multicast router port, and (3) no known IGMP
Version 1 hosts exist on this LAN segment, then no leave message will
be forwarded to the local querier or other upstream multicast router.
Only when the last member requests to leave the group, will the switch
then flood the leave message (as specified in the original mechanism
for IGMP snooping).
• When there is a large number of hosts entering and leaving a multicast
group, IGMP snooping leave-proxy can significantly reduce the
amount of multicast messages and number of state changes that have
to be processed by devices in the upstream multicast tree.