Cisco Systems 3750E manual Configuring the Igmp Throttling Action, Interface-id, 24-28

Chapter 24 Configuring IGMP Snooping and MVR

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	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. The interface can be a Layer 2 port that does not belong to an
		EtherChannel group or a EtherChannel interface.
Step 3
	ip igmp max-groups number	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.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show running-config interface	Verify the configuration.
	interface-id
Step 6
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To remove the maximum group limitation and return to the default of no maximum, use the no ip igmp max-groupsinterface configuration command.

This example shows how to limit to 25 the number of IGMP groups that a port can join.

Switch(config)# interface gigabitethernet1/0/2

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:

•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.

–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.

To prevent the switch from removing the forwarding-table entries, you can configure the IGMP throttling action before an interface adds entries to the forwarding table.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
24-28	OL-9775-02