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EDS-726 Series User’s Manual Featured Functions
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industrial automation protocols, such as Allen-Bradley, EtherNet/IP, Siemens Profibus, and
Foundation Fieldbus HSE (High Speed Ethernet), use multicast. These industrial Ethernet
protocols use publisher/subscriber communications models by multicasting packets that could
flood a network with heavy traffic. IGMP Snooping is used to prune multicast traffic so that it
travels only to those end destinations that require the traffic, reducing the amount of traffic on the
Ethernet LAN.
Multicast Filtering
Multicast filtering ensures that only end-stations that have joined certain groups receive multicast
traffic. With multicast filtering, network devices only forward multicast traffic to the ports that are
connected to registered end-stations. The following two figures illustrate how a network behaves
without multicast filtering, and with multicast filtering.
Network without multicast filtering
12345678
Serial ports
Console LAN
910111213141516
IGMP Group2
Group 1 Multicast Stream Group 2 Multicast Stream
IGMP Group1 IGMP Group2 IGMP Group1
All hosts receive the multicast traffic, even if they don’t need it.
Network with multicast filtering
IGMP Group2
Group 1 Multicast Stream Group 2 Multicast Stream
IGMP Group1 IGMP Group2 IGMP Group1
EDS-726
EtherDevice Switch
34
IM-4TX
12
PWR
P3
P1
P4
P2
IM-4MST
TX
RX
34
TX
RX
1 2
PWR
P3
P1
P4
P2
IM-4MSC
TX
RX
3 4
TX
RX
1 2
PWR
P3
P1
P4
P2
IM-2MST/2TX
TX
RX
34
12
PWR
P3
P1
P4
P2
IM-2MSC/2TX
TX
RX
34
12
PWR
P3
P1
P4
P2
IM-1LSC/3TX
4
12
3
TX
RX
PWR
P3
P1
P4
P2
COUPLERCF
STAT
PWR1 FAULT
MASTER
PWR2
IM-1GSXSCIM-1GTX
MODE
RING
PORT
COUPLER
PORT
FDX/HDX
LNK/ACT
SPEED
Hosts only receive dedicated traffic from other hosts belonging to the same group.