Cisco 4500M Software Manual page 274

Configuring IGMP Snooping
While in "multicast flooding mode," IP multicast traffic is delivered to all ports in the VLAN, and not
restricted to those ports on which multicast group members have been detected.
Starting with 12.1(11b)EW, you can manually prevent IP multicast traffic from being flooded to a
switchport by using the no ip igmp snooping tcn flood command on that port.
For trunk ports, the configuration will apply to all VLANs.
By default, multicast flooding is enabled. Use the no keyword to disable flooding, and use default to
restore the default behavior (flooding is enabled).
To disable multicast flooding on an interface, perform this task:
Command
Step 1
Switch(config)# interface {fastethernet |
gigabitethernet | tengigabitethernet} slot / port
Step 2
Switch(config-if)# no ip igmp snooping tcn flood
Step 3
Switch(config)# end
Step 4
Switch# show running interface {fastethernet |
gigabitethernet | tengigabitethernet} slot / port
This example shows how to disable multicast flooding on interface FastEthernet 2/11:
Switch(config)# interface fastethernet 2/11
Switch(config-if)# no ip igmp snooping tcn flood
Switch(config-if)# end
Switch#
IGMP Snooping Switch Configuration
By default, "flooding mode" persists until the switch receives two IGMP general queries. You can
change this period of time by using the
ip igmp snooping tcn flood query count n command, where n is a number between 1 and 10.
This command operates at the global configuration level.
The default number of queries is 2. The no and default keywords restore the default.
To establish an IGMP query threshold, perform this task:
Command
Step 1
Switch(config)#
ip igmp snooping tcn flood query count <n>
Step 2
Switch(config)# end
Software Configuration Guide—Release 12.2(25)EW
18-10
Chapter 18 Configuring IGMP Snooping and Filtering
Purpose
Selects the interface to configure.
Disables multicast flooding on the interface when TCNs
are received by the switch.
To enable multicast flooding on the interface, enter this
command:
default ip igmp snooping tcn flood
Exits configuration mode.
Verifies the configuration.
Purpose
Modifies the number of IGMP queries the switch will
wait for before it stops flooding multicast traffic.
To return the switch to the default number of IGMP
queries, enter this command:
default ip igmp snooping tcn flood query count .
Exits configuration mode.
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