Chapter 20
| Multicast Filtering Commands
IGMP Snooping
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Command Usage
◆ By default, general query messages are flooded to all ports, except for the
multicast router through which they are received.
◆ If general query suppression is enabled, then these messages are forwarded
only to downstream ports which have joined a multicast service.
Example
Console(config)#ip igmp snooping vlan 1 general-query-suppression
Console(config)#
ip igmp snooping vlan
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 vlan vlan-id immediate-leave
vlan-id - VLAN ID (Range: 1-4093)
Default Setting
Disabled
Command Mode
Global Configuration
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 time out period. (The time out for this release is
currently defined by Last Member Query Interval (fixed at one second) *
Robustness Variable (fixed at 2) as defined in RFC 2236.
◆ 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.
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