206 Rockwell Automation Publication 5069-UM004A-EN-P - April 2019
Chapter 7      Configure and Replace Safety Modules
Replace a Safety Module
Replacing a safety module that sits on a CIP Safety™ network is more 
complicated than replacing standard devices because of the Safety Network 
Number (SNN). 
Safety devices require this more complex identifier to make sure that module 
numbers that are duplicated on separate subnets across all networks in the 
application do not compromise communication between the correct safety 
devices.
The SNN is a unique identifier that is automatically assigned to each subnet in 
a safety application. The same SNN is assigned to all devices on the subnet. 
For example, when a Compact 5000 I/O EtherNet/IP adapter is used in a 
safety application, the Logix Designer application project assigns it an SNN. 
All Compact 5000 I/O digital modules that are installed with that adapter, are 
automatically assigned the same SNN.
However, each Compact 5000 I/O safety modules require a unique identifier 
within the same subnet. A DeviceID is used to uniquely identify each safety 
module. The SNN and module slot number constitute the DeviceID of the 
safety module. 
Set the SNN Manually
The SNN is used to provide integrity on the initial download to a 
Compact 5000 I/O safety module.
If a safety signature exists, the Compact 5000 I/O safety module must have 
DeviceID that matches the module in the safety controller project, before it 
can receive its configuration. 
To maintain integrity, the module SNN must be set manually. 
1. On the General category of the Module Properties dialog box, click the 
ellipsis next to the Safety Network Number.