Recovering From Flood Mode; Disabling Multicast Flooding During A Tcn Event - Cisco IE 3000 Software Configuration Manual
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- Hardware installation manual (186 pages) ,
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Configuring IGMP Snooping
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
Step 3
end
Step 4
show ip igmp snooping
Step 5
copy running-config startup-config
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:
Command
Step 1
configure terminal
Step 2
ip igmp snooping tcn query solicit
Step 3
end
Step 4
show ip igmp snooping
Step 5
copy running-config startup-config
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.
Cisco IE 3000 Switch Software Configuration Guide
21-12
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.
Return to privileged EXEC mode.
Verify the TCN settings.
(Optional) Save your entries in the configuration file.
Purpose
Enter global configuration mode.
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.
Return to privileged EXEC mode.
Verify the TCN settings.
(Optional) Save your entries in the configuration file.
Chapter 21
Configuring IGMP Snooping and MVR
OL-13018-01
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