Juniper ACX1000 Configuration Manual page 532

ACX Series Universal Access Router Configuration Guide
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474
You configure IGMP snooping for each bridge on the router. A bridge instance without
qualified learning has just one learning domain. For a bridge instance with qualified
learning, snooping will function separately within each learning domain in the bridge.
That is, IGMP snooping and multicast forwarding will proceed independently in each
learning domain in the bridge.
This discussion focuses on bridge instances without qualified learning (those forming
one learning domain on the device). Therefore, all the interfaces mentioned are logical
interfaces of the bridge or VPLS instance.
Several related concepts are important when discussing IGMP snooping:
Bridge or VPLS instance interfaces are either multicast-router interfaces or host-side
interfaces.
IGMP snooping supports proxy mode or without-proxy mode.
NOTE: When integrated routing and bridging (IRB) is used, if the router is an
IGMP querier, any leave message received on any Layer 2 interface will cause
a group-specific query on all Layer 2 interfaces (as a result of this practice,
some corresponding reports might be received on all Layer 2 interfaces).
However, if some of the Layer 2 interfaces are also router (Layer 3) interfaces,
reports and leaves from other Layer 2 interfaces will not be forwarded on
those interfaces.
If an IRB interface is used as an outgoing interface in a multicast forwarding cache entry
(as determined by the routing process), then the output interface list is expanded into a
subset of the Layer 2 interface in the corresponding bridge. The subset is based on the
snooped multicast membership information, according to the multicast forwarding cache
entry installed by the snooping process for the bridge.
If no snooping is configured, the IRB output interface list is expanded to all Layer 2
interfaces in the bridge.
The Junos OS does not support IGMP snooping in a VPLS configuration on a virtual switch.
This configuration is disallowed in the CLI.
NOTE: IGMP snooping is supported on AE interfaces, however, it is not
supported on AE interfaces in combination with IRB interfaces.
Multicast Overview
Understanding Multicast Snooping
Example: Configuring IGMP Snooping on page 479
IGMP Snooping in MC-LAG Active-Active Mode
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