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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
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Chapter 26 Configuring IGMP Snooping and MVR Configuring IGMP Snooping
Beginning in privileged EXEC mode, follow these steps to enable the IGMP configurable-leave timer:
To globally reset the IGMP leave timer to the default setting, use the no ip igmp snooping
last-member-query-interval global configuration command.
To remove the configured IGMP leave-time setting from the specified VLAN, use the no ip igmp
snooping vlan vlan-id last-member-query-interval global configuration command.
Configuring TCN-Related Commands
• Controlling the Multicast Flooding Time After a TCN Event, page 26-11
• Recovering from Flood Mode, page 26-12
• Disabling Multicast Flooding During a TCN Event, page 26-12

Controlling the Multicast Flooding Time After a TCN Event

You can control the time that multicast traffic is flooded after a TCN event by using the ip igmp
snooping tcn flood query count global configuration command. This command configures the number
of general queries for which multicast data traffic is flooded after a TCN event. Some examples of TCN
events are when the client changed its location and the receiver is on same port that was blocked but is
now forwarding, and when a port went down without sending a leave message.
If you set the TCN flood query count to 1 by using the ip igmp snooping tcn flood query count
command, the flooding stops after receiving 1 general query. If you set the count to 7, the flooding until
7 general queries are received. Groups are relearned based on the general queries received during the
TCN event.
Beginning in privileged EXEC mode, follow these steps to configure the TCN flood query count:
Command Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2 ip igmp snooping
last-member-query-interval time Configure the IGMP leave timer globally. The range is 100 to
32768 milliseconds. The default is 1000 seconds.
Step 3 ip igmp snooping vlan vlan-id
last-member-query-interval time (Optional) Configure the IGMP leave time on the VLAN interface. The
range is 100 to 32768 milliseconds.
Note Configuring the leave time on a VLAN overrides the globally
configured timer.
Step 4 end Return to privileged EXEC mode.
Step 5 show ip igmp snooping (Optional) Display the configured IGMP leave time.
Step 6 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2 ip igmp snooping tcn flood query count
count Specify the number of IGMP general queries for which the multicast
traffic is flooded. The range is 1 to 10. By default, the flooding query
count is 2.