Immediate Leave; Igmp Configurable-Leave Timer; Igmp Report Suppression - Cisco Catalyst 3850 series Configuration Manual

IGMP Snooping

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.
Note You should use the Immediate Leave feature only on VLANs where a single host is connected to each
port. If Immediate Leave is enabled on VLANs where more than one host is connected to a port, some
hosts may be dropped inadvertently.
Related Topics
Enabling IGMP Immediate Leave (CLI), on page 77

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 32767 milliseconds.
Related Topics
Configuring the IGMP Leave Timer (CLI), on page 78

IGMP Report Suppression

IGMP report suppression is supported only when the multicast query has IGMPv1 and IGMPv2 reports.
Note
This feature is not supported when the query includes IGMPv3 reports.
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 3.6E (Catalyst 3850 Switches)
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Configuring IGMP
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