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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
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Chapter20 Configuring IGMP Snooping and MVR
Configuring IGMP Filtering and Thrott li ng
Beginning in privileged EXEC mode, follow these steps to set the maximum number of IGMP groups in
the forwarding table:
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:
•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 a n Ethe rC hanne l po rt g roup.
•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.
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If you configure the throttling action as deny, the en tries t hat were pre v iously i n the f orwa rding
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 n ext 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 forwar ding table,
the switch replaces a randomly selected entry with the received IGMP report.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 interface interface-id Specify the interface to be configur ed, a nd ente r inte rf ace configuration
mode. The interface can be a Layer 2 port that does no t be long t o an
EtherChannel group or a EtherChannel interface.
Step3 no shutdown Enable the port, if necessary. By default, UNIs are disabled, and NNIs
are enabled.
Step4 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 .
Step5 end Return to privileged EXEC mode.
Step6 show running-config interface
interface-id Verify the configuration.
Step7 copy running-config startup-config (Optional) Save your entries in the configuration file.