Rockwell Automation 1791DS-IBxxxx Guard I/O DeviceNet Safety Modules - Manual (Page 118)

118 Rockwell Automation Publication 1791DS-UM001J-EN-P - May 2013
Chapter 7 Considerations When Replacing Guard I/O Modules
If the replacement module is out-of-box or has an SNN that does not
match the original module, the module appears with an exclamation mark.
3. Right-click the module and choose Download to Device.
This dialog box appears.
4. Click Yes.
This dialog box appears informing you that the SNN of the replacement
module does not match the SNN in the software.
5. Click Download to set the SNN on the replacement module.