Cisco Cisco Gigabit Ethernet Switch Module (CGESM) for HP Technical References

Use the ip igmp snooping tcn global configuration command to configure the Internet Group 
Management Protocol (IGMP) Topology Change Notification (TCN) behavior. Use the no form of this 
command to return to the default settings.

ip igmp snooping tcn {flood query count count | query solicit}

no ip igmp snooping tcn {flood query count | query solicit}

The TCN flood query count is 2.

The TCN query solicitation is disabled.

Global configuration 

Use ip igmp snooping tcn flood query count global configuration command command to control the 
time that multicast traffic is flooded after a TCN event. 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 of multicast traffic due to the TCN event lasts until 
7 general queries are received. Groups are relearned based on the general queries received during the 
TCN event.

Use the ip igmp snooping tcn query solicit global configuration command to enable the switch to send 
the global leave message whether or not it is the spanning-tree root. This command also speeds the 
process of recovering from the flood mode caused during a TCN event.

This example shows how to specify 7 as the number of IGMP general queries for which the multicast 
traffic is flooded:

Switch(config)# no ip igmp snooping tcn flood query count 7

You can verify your settings by entering the show ip igmp snooping privileged EXEC command.

flood query count count

Specify the number of IGMP general queries for which the multicast traffic 
is flooded. The range is 1 to 10.

query solicit 

Send an IGMP leave message (global leave) to speed the process of 
recovering from the flood mode caused during a TCN event.

12.2(25)SE1

This command was introduced.