30 Rockwell Automation Publication 1756-RM012B-EN-P - April 2018
Chapter 4 CIP Safety and Safety Network Numbers
Routable CIP Safety System
The example system in Figure 8 is not interconnected to another CIP Safety
system through a larger, plant-wide Ethernet backbone. Therefore, Figure 8
illustrates the extent of a routable CIP Safety system.
Figure 8 - Safety System Example
In this example:
• For a backplane port, an SNN is assigned to the backplane and the node
address is the slot number of the device.
• For an Ethernet port, an SNN is assigned to the EtherNet/IP network
and the node address is the IP address of the device.
• The 5069-L320ERS2 is in Dual-IP mode and connected to two separate
EtherNet/IP networks. They must not share SNN values because the
switches can incorrectly route packets between them.
Considerations for Assigning
SNNs
When creating controller projects, the Studio 5000 Logix Designer application
generates an SNN value automatically whenever it recognizes a new subnet
that contains CIP Safety devices:
• Each CIP Safety-capable port on the controller is assigned an SNN.
• If a bridge or adapter device is in the I/O tree and a child CIP Safety
device is added, the subnet that is created by the bridge or adapter is
assigned an SNN.
If the entire CIP Safety system consists of one controller project, these
automatically generated SNN values are sufficient.
If there are multiple controllers that must interact or access the same safety
I/O, the CIP Safety system designer must coordinate the SNN values between
the separate project files. The Studio 5000 Logix Designer application provides
copy/paste access to the SNN assignments to enable this coordination.
1769-L36ERMS
5069-OBV8S
Switch Switch
5069-L320ERS2
1732DS-IB6
1732ES-IB16
1732DS-IBSXOBV4
1791ES-IB16
1756-L71S
1756-DNB
1756-L7SP
1756-EN2T
1756-L84ES
1756-L81ES
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