Cisco Catalyst 3750-X Software Configuration Manual page 695

Chapter 26 Configuring IGMP Snooping and MVR
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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
ip igmp max-groups action {deny |
Step 3
replace}
Step 4 end
Step 5 show running-config interface
interface-id
Step 6
copy running-config startup-config
To return to the default action of dropping the report, use the no ip igmp max-groups action interface
configuration command.
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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.
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replace—Replace the existing group with the new group for which
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the IGMP report was received.
Return to privileged EXEC mode.
Verify the configuration.
(Optional) Save your entries in the configuration file.
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
Configuring IGMP Filtering and Throttling
26-27