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Enabling IGMP Immediate Leave
The switch can be configured to immediately delete a member port of a multicast
service if a leave packet is received at that port and the immediate-leave function is
enabled for the parent VLAN. This allows the switch to remove a port from the
multicast forwarding table without first having to send an IGMP group-specific query
to that interface.
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 the IGMP Query Report Delay (see “Configuring IGMP Snooping
and Query Parameters” on page 15-3).
• 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.
• Immediate leave is only effective if IGMP snooping is enabled, and IGMPv2 or
IGMPv3 snooping is used.
• Immediate leave does not apply to a port if the switch has learned that a multicast
router is attached to it.
• Immediate leave can improve bandwidth usage for a network which frequently
experiences many IGMP host add and leave requests.
Command Attributes
• VLAN ID – VLAN Identifier. (Range: 1-4093).
• Immediate Leave – Sets the status for immediate leave on the specified VLAN.
(Default: Disabled)
Web
– Click IGMP Snooping, IGMP Immediate Leave. Select the VLAN interface to
configure, set the status for immediate leave, and click Apply.
Figure 15-1 IGMP Immediate Leave
15-5
Layer 2 IGMP (Snooping and Query)
15