Edge Products ES3528-WDM - Manual (Page 508)

Multicast Filtering Commands
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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.
• IGMP version 1 hosts do not respond to multicast group-specific queries. If a
version 1 host is known by the switch to exist on a LAN segment, it will not use
the IGMP snooping leave-proxy mechanism on that interface, but will instead
process any group leave requests as specified in the original mechanism for
IGMP snooping.
Example
The following shows how to enable leave proxy.
ip igmp snooping immediate-leave
This command immediately deletes a member port of a multicast service if a leave
packet is received at that port and immediate-leave is enabled for the parent VLAN.
Use the no form to restore the default.
Syntax
ip igmp snooping immediate-leave
no ip igmp snooping immediate-leave
Default Setting
Disabled
Console(config)#ip igmp snooping leave-proxy
Console(config)#