Moxa Technologies Moxa EtherDevice Switch EDS-508 - Manual (Page 57)

EDS-508 Series User’s Manual Featured Functions
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publisher/subscriber communications models by multicasting packets that could flood a network
with heavy traffic. IGMP Snooping provides the ability to prune multicast traffic so that it travels
only to those end destinations that require the traffic, thus reducing the amount of traffic on the
Ethernet LAN.
Multicast Filtering
Multicast filtering is the process that ensures that end-stations only receive multicast traffic if they
register to join specific multicast groups. With multicast filtering, network devices only forward
multicast traffic to the ports that are connected to registered end-stations. The following figure
shows how a network behaves without multicast filtering, and with multicast filtering.
The Network without multicast filtering
IGMP Group 1 IGMP Group 1 IGMP Group 2 IGMP Group 2
Group 1 Multicast Stream Group 2 Multicast Stream
All end-stations must handle the traffic whether they need it or not.
The Network with multicast filtering
IGMP Group 1 IGMP Group 1 IGMP Group 2 IGMP Group 2
Group 1 Multicast Stream Group 2 Multicast Stream
End-stations only receive dedicated traffic belonging to the same group.