Omron SYSMAC CJ1W-EIP21, Operation Manuals

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2 Installing Ethernet Networks
2-6
CJ-series EtherNet/IP Units Operation Manual for NJ-series CPU Unit (W495)
Support for the above two functions is as follows for the different types of Ethernet switches.
Additional Information
If the Network Configurator is used to set the connection type in the connection settings to a mul-
ticast connection, multicast packets are used. If the connection type is set to a point-to-point con-
nection, multicast packets are not used.
The functions supported by the Ethernet switch may affect tag data link transmission delays and the
settings in the Controller configurations and setup. In addition, if the Ethernet switch supports advanced
functions, special settings are required for those functions. When you select an Ethernet switch, it is
necessary to consider whether to select the Ethernet switch based on the kind and amount of commu-
nications you want to execute in the network. Refer to the following precautions when you select an
Ethernet switch. Refer to 12-2 Adjusting the Communications Load to estimate the communications
load for tag data links.

Executing Tag Data Links Only
We recommend that you use an L2 Ethernet switch without multicast filtering or an L2 Ethernet
switch with multicast filtering. An L2 Ethernet switch with multicast filtering prevents increased traffic
due to unnecessary multicast packets, so the tag data links can operate at higher speed. If either of
the following conditions exists, the amount traffic will be the same for both kinds of L2 Ethernet
switches (with or without multicast filtering).
• 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.
If multicast filters are being used, settings must be made in the Ethernet switch. There must be
enough multicast filters for the network being used.

Executing Tag Data Links and Message Communications
We recommend an L2 Ethernet switch with multicast filtering and L4 QoS. If you set tag data links
for higher-priority transmission, it is possible to prevent problems such as transmission delays due to
message communications traffic and packet losses due to buffer overflow. You must make special
settings in the Ethernet switch when using the multicast filtering function and L4 QoS function.
Ethernet switch types Multicast filtering L4 QoS Remarks
Unmanaged L2 Ethernet
switches None None ---
Managed L2 Ethernet
switches Provided. Provided. Both functions must be set
with a special software tool.
OMRON W4S1-series
Ethernet switches None Provided. L4 QoS is set with a switch. No
software tool is necessary.
2-3-5 Precautions for Ethernet Switch Selection
Selecting the Ethernet Switch Based on the Types of Network
Communications