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Catalyst 3750 MetroSwitch Software Configuration Guide
78-15870-01
Chapter 17 Configuring IGMP Snooping and MVR
Configuring IGMP Filtering
Configuring IGMP Filtering
In some environments, for example metropolitan or multiple-dwelling unit (MDU) installations, an
administrator might want to control the set of multicast groups to which a user on a switch port can
belong. This allows the administrator to control the distribution of multicast services, such as IP/TV,
based on some type of subscription or service plan. With the IGMP filtering feature, you can filter
multicast joins on a per-port basis by configuring IP multicast profiles and associating them with
individual switch ports. An IGMP profile can contain one or more multicast groups and specifies
whether access to the group is permitted or denied. If an IGMP profile denying access to a multicast
group is applied to a switch port, the IGMP join report requesting the stream of IP multicast traffic is
dropped, and the port is not allowed to receive IP multicast traffic from that group. If the filtering action
permits access to the multicast group, the IGMP report from the port is forwarded for normal processing.
IGMP filtering controls only group specific query and membership reports, including join and leave
reports. It does not control general IGMP queries. IGMP filtering has no relationship with the function
that directs the forwarding of IP multicast traffic. The filtering feature operates in the same manner
whether CGMP or MVR is used to forward the multicast traffic.
IGMP filtering is only applicable to dynamic learning of IP multicast group addresses; not static
configuration.
You can also set the maximum number of IGMP groups that a Layer 2 interface can join.
Default IGMP Filtering Configuration
Table 17-7 shows the default IGMP filtering configuration.
Configuring 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 this 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 the profile by using these commands:
• deny: Specifies that matching addresses are denied; this is the default condition.
• exit: Exits from igmp-profile configuration mode.
• no: Negates a command or sets 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 range
with a start and an end address.
Table 17-7 Default IGMP Filtering Configuration
Feature Default Setting
IGMP filters None applied
IGMP Maximum number of IGMP groups No maximum set
IGMP profiles None defined
IGMP profile action Deny the range addresses
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