Igmp Snooping Interfaces And Forwarding; Igmp Snooping And Proxies - Juniper ACX1000 Configuration Manual

IGMP Snooping Interfaces and Forwarding

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IGMP Snooping and Proxies

Copyright © 2017, Juniper Networks, Inc.
IGMP snooping divides the device interfaces into multicast-router interfaces and host-side
interfaces. A multicast-router interface is an interface in the direction of a multicasting
router. An interface on the bridge is considered a multicast-router interface if it meets at
least one of the following criteria:
It is statically configured as a multicast-router interface in the bridge instance.
IGMP queries are being received on the interface.
All other interfaces that are not multicast-router interfaces are considered host-side
interfaces.
Any multicast traffic received on a bridge interface with IGMP snooping configured will
be forwarded according to following rules:
Any IGMP packet is sent to the Routing Engine for snooping processing.
Other multicast traffic with destination address 224.0.0/24 is flooded onto all other
interfaces of the bridge.
Other multicast traffic is sent to all the multicast-router interfaces but only to those
host-side interfaces that have hosts interested in receiving that multicast group.
Multicast Overview
Understanding Multicast Snooping
Without a proxy arrangement, IGMP snooping does not generate or introduce queries
and reports. It will only "snoop" reports received from all of its interfaces (including
multicast-router interfaces) to build its state and group (S,G) database.
Without a proxy, IGMP messages are processed as follows:
Query—All general and group-specific IGMP query messages received on a
multicast-router interface are forwarded to all other interfaces (both multicast-router
interfaces and host-side interfaces) on the bridge.
Report—IGMP reports received on any interface of the bridge are forwarded toward
other multicast-router interfaces. The receiving interface is added as an interface for
that group if a multicast routing entry exists for this group. Also, a group timer is set for
the group on that interface. If this timer expires (that is, there was no report for this
group during the IGMP group timer period), then the interface is removed as an interface
for that group.
Leave—Any IGMP leave message received on any interface of the bridge. The Leave
Group message reduces the time it takes for the multicast router to stop forwarding
multicast traffic when there are no longer any members in the host group.
Chapter 15: Configuring Internet Group Management Protocol Snooping
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