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Catalyst 2960 Switch SoftwareConfiguration Guide
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Chapter20 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
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
These sections describe how to control flooded multicast traffic during a TCN event:
•Controlling the Multicast Flooding Time After a TCN Event, page 20-11
•Recovering from Flood Mode, page 20-12
•Disabling Multicast Flooding During a TCN Event, page 20-12

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 la sts
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 fl ood query count:
To return to the default flooding query count, use the no ip igmp snooping tcn flood query count global
configuration command.
Step5 show ip igmp snooping (Optional) Display the configured IGMP leave time.
Step6 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 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.
Step3 end Return to privileged EXEC mode.
Step4 show ip igmp snooping Verify the TCN settings.
Step5 copy running-config startup-config (Optional) Save your entries in the configuration file.