Configuring The Igmp Throttling Action - Cisco Catalyst 2960 Software Configuration Manual
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Configuring IGMP Filtering and Throttling
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 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:
•
•
•
Beginning in privileged EXEC mode, follow these steps to configure the throttling action when the
maximum number of entries is in the forwarding table:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
ip igmp max-groups action {deny |
replace}
Catalyst 2960 and 2960-S Switches Software Configuration Guide, Release 15.0(1)SE
21-28
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.
Purpose
Enter global configuration mode.
Specify the physical 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 an EtherChannel interface. The
interface cannot be a trunk port.
When an interface receives an IGMP report and the maximum number
of entries is in the forwarding table, specify the action that the interface
takes:
deny—Drop the report.
•
replace—Replace the existing group with the new group for which
•
the IGMP report was received.
Chapter 21
Configuring IGMP Snooping and MVR
OL-26520-01
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