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Configuring IGMP Filtering and Throttling
Beginning in privileged EXEC mode, follow these steps to set the maximum number of IGMP groups in
the forwarding table:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
no shutdown
Step 4
ip igmp max-groups number
Step 5
end
Step 6
show running-config interface
interface-id
Step 7
copy running-config startup-config
To remove the maximum group limitation and return to the default of no maximum, use the no ip igmp
max-groups interface configuration command.
This example shows how to limit to 25 the number of IGMP groups that a port can join.
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# ip igmp max-groups 25
Switch(config-if)# end
Configuring the IGMP Throttling Action
After you set the maximum number of IGMP groups that a Layer 2 interface can join, you can configure
an interface to replace the existing group with the new group for which the IGMP report was received
by using the ip igmp max-groups action replace interface configuration command. Use the no form of
this command to return to the default, which is to drop the IGMP join report.
Follow these guidelines when configuring the IGMP throttling action:
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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
20-26
This restriction can be applied only to Layer 2 ports. You can use this command on a logical
EtherChannel interface but cannot use it on ports that belong to an EtherChannel port group.
When the maximum group limitation is set to the default (no maximum), entering the ip igmp
max-groups action {deny | replace} command has no effect.
If you configure the throttling action and set the maximum group limitation after an interface has
added multicast entries to the forwarding table, the forwarding-table entries are either aged out or
removed, depending on the throttling action.
If you configure the throttling action as deny, the entries that were previously in the forwarding
–
table are not removed but are aged out. After these entries are aged out and the maximum
number of entries is in the forwarding table, the switch drops the next IGMP report received on
the interface.
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If you configure the throttling action as replace, the entries that were previously in the
forwarding table are removed. When the maximum number of entries is in the forwarding table,
the switch replaces a randomly selected entry with the received IGMP report.
Purpose
Enter global configuration mode.
Specify the interface to be configured, and enter interface configuration
mode. The interface can be a Layer 2 port that does not belong to an
EtherChannel group or a EtherChannel interface.
Enable the port, if necessary. By default, UNIs are disabled, and NNIs
are enabled.
Set the maximum number of IGMP groups that the interface can join.
The range is 0 to 4294967294. The default is to have no maximum set.
Return to privileged EXEC mode.
Verify the configuration.
(Optional) Save your entries in the configuration file.
Chapter 20
Configuring IGMP Snooping and MVR
78-17058-01
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