Troubleshoot The Module - Allen-Bradley E Series Installation Instructions Manual

The 1786-CP cable can be plugged into any ControlNet network product's
network access port (NAP) to provide programming capability on the
ControlNet network. A programming terminal connected through this cable
is counted as a node and must have a unique network address.
Use a 1786-CP cable when connecting a programming terminal to the
ATTENTION
network through network access port (NAP). Using a commercially
available RJ-style cable could result in network failure.

Troubleshoot the Module

The 1756-CNB and 1756-CNBR modules have the diagnostic indicators as
shown:
1756-CNB
ControlLogix ControlNet Interface Module 23
1756-CNBR
ControlNet Channel Status
Indicators - See Page 28.
Channel A BNC Connector
Channel B BNC Connector
Publication
1756-IN604A-EN-P - February 2006
Module Status Display - See
Pages 24 to 27.
Module Status Indicator -
See Pages 24 to 27.