Multicast Filtering Commands

4-269

4
The IGMP snooping leave-proxy feature suppresses all unnecessary IGMP
leave messages so that the non-querier switch forwards an IGMP leave
packet only when the last dynamic member port leaves a multicast group.
The leave-proxy feature does not function when a switch is set as the querier.
When the switch a non-querier, the receiving port is not the last dynamic
member port in the group, the receiving port is not a router port, and no
IGMPv1 member port exists in the group, the switch will generate and send a
GS-query to the member port which received the leave message, and then
start the last member query timer for that port.
When the conditions in the preceding item all apply, except that the receiving
port is a router port, then the switch will not send a GS-query, but will
immediately start the last member query timer for that port.
Example

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
[no] ip igmp snooping immediate-leave
Default Setting
Disabled
Command Mode
Interface Configuration (VLAN)
Command Usage
If immediate-leave is not used, a multicast router (or querier) will send a
group-specific query message when an IGMPv2/v3 group leave message is
received. The router/querier stops forwarding traffic for that group only if no
host replies to the query within the specified timeout period. Note that the
timeout period is determined by ip igmp snooping
query-max-response-time (see 4-273).
If immediate-leave is enabled, the switch assumes that only one host is
connected to the interface. Therefore, immediate leave should only be
enabled on an interface if it is connected to only one IGMP-enabled device,
either a service host or a neighbor running IGMP snooping.
This command is only effective if IGMP snooping is enabled, and IGMPv2 or
IGMPv3 snooping is used.
Console(config)#ip igmp snooping leave-proxy
Console(config)#