Hi all,
Can you help me in how to establish a OPC UA server communication between S7-400 PLC and CP-443-1 (not a OPC UA module) so that the CP-443-1 module can be set as a OPC UA server and the Client will be Ignition where it can access the data. 

Dear

S7 400 CPU not Support OPC UA, If you want data to OPC you can add S71200 to ET200SP CPU as OPC Gateway.

Thank

Hello AutoGen_bd808

If you want to communicate between two S7-400 PLCs there are other ways than OPC.

S7300/400 do not support OPC UA direcly on the PLC such as a S71200/1500.

you can use a SIMATIC Net OPC Server for accessing the PLCs but the communication between the OPC Server and the PLC runs via S7protocol:

https://support.industry.siemens.com/cs/ww/en/view/67295801

If you give us a few more information about your usecase and your requirments perhaps there are other ways to do it...

Bye Murof