Cisco Catalyst 3750-E Software Configuration Manual page 646

Configuring IGMP Snooping
Beginning in privileged EXEC mode, follow these steps to enable the IGMP configurable-leave timer:
Command
Step 1
configure terminal
Step 2
ip igmp snooping
last-member-query-interval time
Step 3
ip igmp snooping vlan vlan-id
last-member-query-interval time
Step 4 end
Step 5 show ip igmp snooping
Step 6 copy running-config startup-config
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
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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
Step 1 configure terminal
Step 2 ip igmp snooping tcn flood query count
count
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
24-12
Controlling the Multicast Flooding Time After a TCN Event, page 24-12
Recovering from Flood Mode, page 24-13
Disabling Multicast Flooding During a TCN Event, page 24-13
Purpose
Enter global configuration mode.
Configure the IGMP leave timer globally. The range is 100 to
32768 milliseconds. The default is 1000 seconds.
(Optional) Configure the IGMP leave time on the VLAN interface. The
range is 100 to 32768 milliseconds.
Configuring the leave time on a VLAN overrides the globally
Note
configured timer.
Return to privileged EXEC mode.
(Optional) Display the configured IGMP leave time.
(Optional) Save your entries in the configuration file.
Purpose
Enter global configuration mode.
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.
Chapter 24 Configuring IGMP Snooping and MVR
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