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Catalyst 2940 Switch Software Configuration Guide
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Chapter 16 Configuring IGMP Snooping and MVR
Configuring IGMP Filtering and Throttling
This is an example of output from the show mvr interface privileged EXEC command for a specified
interface:
Switch# show mvr interface fastethernet0/2
224.0.1.1 DYNAMIC ACTIVE
This is an example of output from the show mvr interface privileged EXEC command when the
members keyword is included:
Switch# show mvr interface fastethernet0/2 members
224.0.1.1 DYNAMIC ACTIVE
This is an example of output from the show mvr members privileged EXEC command:
Switch# show mvr members
MVR Group IP Status Members
------------ ------ -------
224.0.1.1 ACTIVE Fa0/1(s), Fa0/2(d)
224.0.1.2 ACTIVE Fa0/1(s)
224.0.1.3 ACTIVE Fa0/1(s)
224.0.1.4 ACTIVE Fa0/1(s)
224.0.1.5 ACTIVE Fa0/1(s)
<output truncated>
Configuring IGMP Filtering and Throttling
In some environments, for example, metropolitan or multiple-dwelling unit (MDU) installations, you
might want to control the set of multicast groups to which a user on a switch port can belong. You can
control the distribution of multicast services, such as IP/TV, based on some type of subscription or
service plan. You might also want to limit the number of multicast groups to which a user on a switch
port can belong.
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.
Note IGMPv3 join and leave messages are not supported on switches running IGMP filtering.
You can also set the maximum number of IGMP groups that a Layer 2 interface can join.
With the IGMP throttling feature, you can also set the maximum number of IGMP groups that a Layer 2
interface can join. If the maximum number of IGMP groups is set, the IGMP snooping forwarding table
contains the maximum number of entries, and the interface receives an IGMP join report, you can
configure an interface to drop the IGMP report or to remove a randomly selected multicast entry in the
forwarding table and then to add the IGMP group in the report to the table.