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Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-08
Chapter 24 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
To return to the default flooding query count, use the
no ip igmp snooping tcn
flood query count
global
configuration command.
Recovering from Flood Mode
When a topology change occurs, the spanning-tree root sends a special IGMP leave message (also known
as global leave) with the group multicast address 0.0.0.0. However, when you enable the
ip igmp
snooping tcn query solicit
global configuration command, the switch sends the global leave message
whether or not it is the spanning-tree root. When the router receives this special leave, it immediately
sends general queries, which expedite the process of recovering from the flood mode during the TCN
event. Leaves are always sent if the switch is the spanning-tree root regardless of this configuration
command. By default, query solicitation is disabled.
Beginning in privileged EXEC mode, follow these steps to enable the switch to send the global leave
message whether or not it is the spanning-tree root:
To return to the default query solicitation, use the
no ip igmp snooping tcn
query solicit
global
configuration command.
Disabling Multicast Flooding During a TCN Event
When the switch receives a TCN, multicast traffic is flooded to all the ports until 2 general queries are
received. If the switch has many ports with attached hosts that are subscribed to different multicast
groups, this flooding might exceed the capacity of the link and cause packet loss. You can use the
ip
igmp snooping tcn flood
interface configuration
command to control this behavior.
Beginning in privileged EXEC mode, follow these steps to disable multicast flooding on an interface:
Step 3
end
Return to privileged EXEC mode.
Step 4
show ip igmp snooping
Verify the TCN settings.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Command
Purpose
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
ip igmp snooping tcn
query solicit
Send an IGMP leave message (global leave) to speed the process of
recovering from the flood mode caused during a TCN event. By
default, query solicitation is disabled.
Step 3
end
Return to privileged EXEC mode.
Step 4
show ip igmp snooping
Verify the TCN settings.
Step 5
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
interface
interface-id
Specify the interface to be configured, and enter interface
configuration mode.
Содержание Catalyst 3750-E Series
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