Immediate-Leave Processing; Cli: Enabling Igmp Immediate-Leave Processing - Cisco Catalyst 2950 Software Manual

Chapter 11 Configuring IGMP Snooping and MVR
Command
Step 4
show ip igmp snooping [vlan vlan-id] Display snooping configuration.
Step 5 copy running-config startup-config
To disable IGMP snooping on a VLAN interface, use the no ip igmp snooping vlan vlan-id global
configuration command for the specified VLAN number (for example, vlan1).
For CLI procedures, refer to the Cisco IOS Release 12.1 documentation on Cisco.com for additional
information and CLI procedures.

Immediate-Leave Processing

IGMP snooping Immediate-Leave processing allows the switch to remove an interface that sends a leave
message from the forwarding table without first sending out MAC-based general queries to the interface.
The VLAN interface is pruned from the multicast tree for the multicast group specified in the original
leave message. Immediate-Leave processing ensures optimal bandwidth management for all hosts on a
switched network, even when multiple multicast groups are in use simultaneously.
You should use the Immediate-Leave processing feature only on VLANs where only one host is
Note
connected to each port. If Immediate-Leave is enabled on VLANs where more than one host is connected
to a port, some hosts might be inadvertently dropped. Immediate Leave is supported only with IGMP
version 2 hosts.

CLI: Enabling IGMP Immediate-Leave Processing

When you enable IGMP Immediate-Leave processing, the switch immediately removes a port from the
IP multicast group when it detects an IGMP version 2 leave message on that port. Immediate-Leave
processing allows the switch to remove an interface that sends a leave message from the forwarding table
without first sending out group-specific queries to the interface. You should use the Immediate-Leave
feature only when there is only a single receiver present on every port in the VLAN.
Beginning in privileged EXEC mode, follow these steps to enable IGMP Immediate-Leave processing:
Command
Step 1
configure terminal
Step 2
ip igmp snooping vlan vlan-id
immediate-leave
Step 3
end
To disable Immediate-Leave processing, follow Steps 1 and 2 to enter interface configuration mode, and
use the no ip igmp snooping vlan vlan-id immediate-leave global configuration command.
For CLI procedures, refer to the Cisco IOS Release 12.1 documentation on Cisco.com for additional
information and CLI procedures.
78-11380-03
Purpose
(Optional) vlan-id is the number of the VLAN.
(Optional) Save your configuration to the startup configuration.
Purpose
Enter global configuration mode.
Enable IGMP Immediate-Leave processing on the VLAN interface.
Return to privileged EXEC mode.
Catalyst 2950 Desktop Switch Software Configuration Guide
Understanding and Configuring IGMP Snooping
11-3