Juniper JUNOS OS 10.4 - FOR EX REV 1 Manual page 2641

Copyright © 2010, Juniper Networks, Inc.
VLAN interface (RVI) to perform these routing functions. IGMP snooping works with Layer
2 interfaces and RVIs to regulate multicast traffic in a switched network.
When a switch receives a multicast packet, the Packet Forwarding Engines in the switch
perform an IP multicast lookup on the multicast packet to determine how to forward the
packet to its local ports. From the results of the IP multicast lookup, each Packet
Forwarding Engine extracts a list of Layer 3 interfaces (which can include VLAN interfaces)
that have ports local to the Packet Forwarding Engine. If an RVI is part of this list, the
switch provides a bridge multicast group ID for each RVI to the Packet Forwarding Engine.
A bridge multicast ID is assigned to direct Layer 3 interfaces and to RVIs. For VLANs that
include multicast receivers, the bridge multicast ID includes a sub-next-hop ID. The
sub-next-hop ID identifies the multicast Layer 2 interfaces in that VLAN that are interested
in receiving the multicast stream. The switch ultimately assigns a next hop after it does
a route lookup. The next hop includes all direct Layer 3 interfaces and RVIs. The Packet
Forwarding Engine then forwards multicast traffic to the bridge multicast ID that includes
all Layer 3 interfaces and RVIs that are multicast receivers for a given multicast group.
Figure 51 on page 2538 shows how multicast traffic is forwarded on a multilayer switch. In
this illustration, multicast traffic is coming in through the
group has been formed by the Layer 3 interface
ge-2/0/0.0 interface is a common trunk interface that belongs to both
The letter "R" next to an interface name in the illustration indicates that a multicast
receiver host is associated with that interface.
NOTE: Traffic sent to an access interface is untagged; traffic sent to a trunk
interface is tagged. For more information on VLAN tagging, see
"Understanding Bridging and VLANs on EX Series Switches" on page 1501.
Chapter 81: Understanding IGMP Snooping and Multicast
xe-0/1/0.0
, , and
ge-0/0/2.0 vlan.0
interface. A multicast
. The
vlan.1
vlan.0 and vlan.1 .
2537