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ip igmp explicit-tracking
Accepting IGMP Reports from Remote Subnetworks
Copyright © 2010, Juniper Networks, Inc.
When you enable explicit host tracking on an interface that has a membership state, the
router does not immediately start performing immediate leave. For a maximum of group
membership interval seconds, the router only performs host tracking. Any leave messages
that the router receives during this period receive normal leave processing. Any leave
messages received after this interval has elapsed receive immediate leave processing,
when appropriate.
When explicit host tracking has been enabled on an IGMP V3 interface, even if a group
has to downgrade to IGMP V2 due to the presence of an IGMP V2 host, explicit host
tracking continues for that group. To avoid this, you can use the
disable-if-igmp-v2-detected keyword. If you select this option, the router turns off explicit
host tracking for the group when IGMP V2 host reports are received for the group on that
interface. This option does not have any significance on an interface configured for IGMP
V2 and is ignored if provided. Because IGMP V1 does not support leave messages, explicit
host tracking is turned off for a group that downgrades to IGMP V1 due to the presence
of IGMP V1 hosts.
Explicit host tracking cannot be enabled on an interface that has immediate-leave
configured and vice versa. Any attempt to configure immediate-leave on an interface
that has explicit host tracking enabled or to configure explicit host tracking on an interface
that has immediate-leave enabled is rejected and an error message logged on the screen.
The following example enables IGMP V3 explicit host tracking on interface 3/0.101 with
the default configuration where the router continues to perform explicit host tracking for
IGMP V2 groups. To override this default configuration, you must use the ip igmp
explicit-tracking disable-if-igmp-v2-detected command.
interface 3/0.101
ip igmp version 3
ip igmp explicit-tracking
end
Use to set explicit host tracking for IP IGMP interfaces.
To disable explicit host tracking if IGMP V2 hosts are detected, use the
disable-if-igmp-v2-detected keyword.
Example
host1(config)#ip igmp explicit-tracking
Use the no version to disable explicit host tracking on the interface. Use the no version
with the disable-if-igmp-v2-detected keyword to revert to the default explicit host
tracking behavior.
See ip igmp explicit-tracking.
By default, IGMP interfaces accept IGMP reports only from associated subnetworks. You
can configure the router to accept IGMP reports from subnetworks that are not associated
Chapter 2: Configuring IGMP
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