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Cisco IE 2000 Switch Software Configuration Guide
OL-25866-01
Chapter 28 Configuring IGMP Snooping and MVR
Information About IGMP Snooping and MVR
IGMP Profiles
To configure an IGMP profile, use the ip igmp profile global configuration command with a profile
number to create an IGMP profile and to enter IGMP profile configuration mode. From thi s mode, you
can specify the parameters of the IGMP profile to be used for filtering IGMP join requests from a port.
When you are in IGMP profile configuration mode, you can create th e profile by using these commands:
• deny—Specifies that matching addresses are denied; this is the default.
• exit—Exits from igmp-profile configuration mode.
• no—Negates a command or returns to its defaults.
• permit—Specifies that matching addresses are permitted.
• range—Specifies a range of IP addresses for the profile. You can enter a single IP address or a ran ge
with a start and an end address.
The default is for the switch to have no IGMP profiles configured. When a profile is configured, if
neither the permit nor deny keyword is included, the default is to deny access to the range of IP
addresses.
To control access as defined in an IGMP profile, use the ip igmp filter interface configuration command
to apply the profile to the appropriate interfaces. You can apply IGMP profiles only to Layer 2 access
ports; you cannot apply IGMP profiles to routed ports or SVIs. You cannot apply profiles to ports th at
belong to an EtherChannel port group. You can apply a profile to multiple interfaces, but each interface
can have only one profile applied to it.
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.
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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 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 forwardi ng 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.