Omron SYSMAC CJ1W-EIP21, Operation Manuals

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2 Installing Ethernet Networks
CJ-series EtherNet/IP Units Operation Manual for NJ-series CPU Unit (W495)
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2-3-5 Preca
utions f
or Ether
net Switch Selection

L2 Ethernet Switch without Multicast Filtering
We recommend this kind of Ethernet switch when only tag data links are executed and any of the fol-
lowing conditions is met.
• The tag data links are set to share the same data with all nodes in the network. (The multicast
packets are transferred to all nodes in the network, just like a broadcast.)
• The tag data link settings are all one-to-one (unicast) and multicast packets cannot be used.
• There is little traffic in the tag data links.
No special settings are required for an L2 Ethernet switch without multicast filtering.

L2 Ethernet Switch with Multicast Filtering
We recommend this kind of Ethernet switch when only tag data links are executed and the following
condition is met.
• There are many 1:N links (where N represents some number of nodes in the network) in the tag
data link settings, i.e., there are many multicast packets used, or there is heavy traffic in the tag
data links.
Special settings are required for an L2 Ethernet switch with multicast filtering. There must be enough
multicast filters for the network.

L3 Ethernet Switch with Multicast Filtering and L4 QoS Functions
We recommend this kind of Ethernet switch when both tag data links and message communications
are executed. If you set tag data links for higher-priority transmission, you can prevent problems
such as transmission delays due to message communications traffic and packet losses due to buffer
overflow. Special settings must be made in the Ethernet switch when using the multicast filtering
function and L4 QoS function. There must be enough multicast filters for the network.
Precautions for Correct Use Precautions for Correct Use
• Ask the Ethernet switch manufacturer for setting procedures for the Ethernet switch.
• Install the Ethernet switch so that its environmental resistance specifications are not
exceeded. Ask the Ethernet switch manufacturer for information on the environmental resis-
tance of the Ethernet switch.
Selecting the Ethernet Switch Based on the Ethernet Switch’s
Supported Functions