Allen-Bradley AB QUALITY ControlLogix 1756 Series User Manual page 78

Your display should appear similar to that below. You should see the
PLC-5/40C processor at node 10 connected to channel B of the left
DHRIO module and the PLC-5/40C processor at node 1 connected to
channel A of the right DHRIO module.
If the PLC-5/40 processors do not appear, then verify the switch settings in
the 1756 DHRIO modules and PLC-5/40 processors and check that the
cables are properly connected.
If you are still experiencing difficulty, reconfigure the routing tables and
Ethernet modules as described previously.
Publication 1756-6.5.13 - September 1999
9-13