Rockwell Automation Publication 1756-UM022D-EN-P - May 2017 57
Chapter 4
Communicate over Networks
The Safety Network
The CIP Safety protocol is an end-node to end-node safety protocol that
provides routing of CIP Safety messages to and from safety I/O devices
through bridges, switches, and routers.
To maintain high integrity when routing through standard bridges, switches, or
routers, each end node within a routable CIP Safety Control System must have
a unique reference. This unique reference is a combination of a safety network
number (SNN) and the node address of the network device.
Manage the Safety Network Number (SNN)
The SNN assigned to safety devices on a network segment must be unique.
You must be sure that a unique SNN is assigned to the following:
• Each CIP Safety network that contains safety devices
• Each chassis that contains one or more GuardLogix® controllers
Topic Page
The Safety Network 57
EtherNet/IP Communication 65
ControlNet Communication 70
DeviceNet Communication 73
TIP Multiple safety network numbers can be assigned to a CIP Safety subnet
or a ControlBus chassis that contains more than one safety device.
However, for simplicity, we recommend that each CIP Safety subnet has
only one unique SNN.
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