Hi Everyone,

I have some questions regarding communication between PLC. Currently we have a systems running with 4 PLC S7-1516F. We configure it as such :

- PLC A (X1 Interface is IO controller)

- PLC B (X1 Interface is IO Controller and X2 Interface is IO Device)

- PLC C (X1 Interface is IO Controller and X2 Interface is IO Device)

- PLC D (X1 Interface is IO Controller and X2 Interface is IO Device)

PLC A Communicate with PLC B, PLC C, and PLC D using X1 of PLC A and X2 on the other PLC. 

Since we are not allowed to have X1 and X2 interface with the same subnet, the local IO of PLC B, PLC C and PLC D is not visible from PLC A X1 Subnet.

Looking at the diagram in manual, we assume we that need to separate between the interface that controls the IO and the interface that communicate with a higher level controller but the more I read into the manual, there's no mentions that I do need to separate it.

Do I need to use X2 to communicate to a higher level controller or can I use X1 on my PLC B to communicate to the higher level controller and my local IO devices?

Thank you all

Below is the manual I've been using :

https://support.industry.siemens.com/cs/ww/en/view/109478798