Immediate Leave
The device uses IGMP snooping Immediate Leave to remove from the forwarding table an interface that sends
a leave message without the device sending group-specific queries to the interface. The VLAN interface is
pruned from the multicast tree for the multicast group specified in the original leave message. Immediate
Leave ensures optimal bandwidth management for all hosts on a switched network, even when multiple
multicast groups are simultaneously in use.
Immediate Leave is only supported on IGMP version 2 hosts. IGMP version 2 is the default version for the
device.
You should only use the Immediate Leave feature on VLANs where a single host is connected to each
port. If Immediate Leave is enabled in VLANs where more than one host is connected to a port, some
hosts might inadvertently be dropped.
Note
IGMP Configurable-Leave Timer
You can configure the time that the device waits after sending a group-specific query to determine if hosts
are still interested in a specific multicast group. The IGMP leave response time can be configured from 100
to 5000 milliseconds. The timer can be set either globally or on a per-VLAN basis. The VLAN configuration
of the leave time overrides the global configuration.
Related Topics
Configuring the IGMP Leave Timer (CLI), on page 65
IGMP Report Suppression
IGMP report suppression is supported only when the multicast query has IGMPv1 and IGMPv2 reports.
This feature is not supported when the query includes IGMPv3 reports.
Note
The device uses IGMP report suppression to forward only one IGMP report per multicast router query to
multicast devices. When IGMP report suppression is enabled (the default), the device sends the first IGMP
report from all hosts for a group to all the multicast routers. The device does not send the remaining IGMP
reports for the group to the multicast routers. This feature prevents duplicate reports from being sent to the
multicast devices.
If the multicast router query includes requests only for IGMPv1 and IGMPv2 reports, the device forwards
only the first IGMPv1 or IGMPv2 report from all hosts for a group to all the multicast routers.
If the multicast router query also includes requests for IGMPv3 reports, the device forwards all IGMPv1,
IGMPv2, and IGMPv3 reports for a group to the multicast devices.
If you disable IGMP report suppression, all IGMP reports are forwarded to the multicast routers.
IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3650 Switches)
OL-29890-01 31
Configuring IGMP
IGMP Snooping
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