How Igmp Snooping Works With Routed Vlan Interfaces - Juniper JUNOS OS 10.4 - FOR EX REV 1 Manual

Complete Software Guide for Junos

How IGMP Snooping Works with Routed VLAN Interfaces

2536
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OS for EX Series Ethernet Switches, Release 10.4
address can never be the source address for a packet. As a result, the switch floods
multicast traffic on the VLAN, consuming significant amounts of bandwidth.
IGMP snooping regulates multicast traffic on a VLAN to avoid flooding. When IGMP
snooping is enabled, the switch intercepts IGMP packets and uses the content of the
packets to build a multicast cache table. The cache table is a database of multicast
groups and their corresponding member ports. The cache table is then used to regulate
multicast traffic on the VLAN.
When the switch receives multicast packets, it uses the cache table to selectively forward
the packets only to the ports that are members of the destination multicast group. Figure
50 on page 2536 shows an example of IGMP traffic flow with IGMP snooping enabled.
Figure 50: IGMP Traffic Flow with IGMP Snooping Enabled
Switches send traffic to hosts that are part of the same broadcast domain, but routers
are needed to route traffic from one broadcast domain to another. Switches use a routed
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