Igmp Snooping And Device Stacks; Igmp Filtering And Throttling Overview; Default Igmp Configuration - Cisco Catalyst 3650 Configuration Manual

Default IGMP Configuration

IGMP Snooping and Device Stacks

IGMP snooping functions across the device stack; that is, IGMP control information from one device is
distributed to all devices in the stack. Regardless of the stack member through which IGMP multicast data
enters the stack, the data reaches the hosts that have registered for that group.
If a device in the stack fails or is removed from the stack, only the members of the multicast group that are
on that device will not receive the multicast data. All other members of a multicast group on other devices in
the stack continue to receive multicast data streams. However, multicast groups that are common for both
Layer 2 and Layer 3 (IP multicast routing) might take longer to converge if the active device is removed.

IGMP Filtering and Throttling Overview

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 device 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 device 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 device 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 device 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.
You can also set the maximum number of IGMP groups that a Layer 2 interface can join.
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 applies only to the dynamic learning of IP multicast group addresses, not static configuration.
With the IGMP throttling feature, you can 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 replace the randomly selected multicast entry with the received IGMP report.
IGMPv3 join and leave messages are not supported on devices running IGMP filtering.
Note
Related Topics
Configuring the IGMP Throttling Action (CLI), on page 50
Examples: Configuring Filtering and Throttling, on page 82
Default IGMP Configuration
This table displays the default IGMP configuration for the device.
IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3650 Switches)
32
Configuring IGMP
OL-29890-01