communication ethernet

[nadjim]

Hello,

I have two plc siemens (CPU 318-2) and another Allen bradley who are in different subnets. I need to get them to communicate with each other on an ethernet network to do interlock. I don't know what to do and what to add as material ??

Thank you

[Admin]

First of all, and most importantly, do not ever use default IP addresses that were set when the 3 PLCs arrived. (never use default IP addresses [channels] on any device for industrial network security. That makes your industrial network/company an easier hacker target, thus more likely, because they can look up IP address in manual, saving them time and bandwidth during their exploration.)

You want to go to each PLC, and set all 3 for the same channel. (IE: in IP 192.168.1.3 the "1" is the channel number. So all 3 PLC IP addresses need to have those first 3 blocks of numbers the same, with the last number [node address] being unique for each PLC.) this is the first step in networking PLCs, "Map out your network.

Example:

Siemens PLC 1            = 192.168.1.3
Siemens PLC 2            = 192.168.1.4
Allen Bradley PLC 1     = 192.168.1.5

To change the IP address in a PLC, go to settings of the module with Ethernet port on it. Like on an AB PLC, you may have Ethernet port on main processor, so to change ip address, you would go to controller settings/communications. Note you will also need to go to PLC vendor's communication software and change the IP address there too, to match the new IP addresses of of each PLC. Like with Rockwell/Allen Bradley, it would be RSLinx software. If the Ethernet port was on a Ethernet module, then you would navigate to the module settings, to change the IP address.

For more see the first video in the free online PLC networking course. This courses walks you through live process of networking PLCs.

[nadjim]

Thank you for all explanations, you really enlightened me.

My two siemens PLCs have two addresses like 192.168.1.38 et 192.168.1.142, and PLC Allen Bradley has another address that is completely different from the other two because it is on another subnet. Should I add another ethernet card on this PLC so that it can have an address similar to the other two ?

My two siemens PLC have the CP 343-1 for ethernet communication and they have on "Use router" two different addresses. Is it a problem so they can communicate ?

Thank you

[Admin]

Go through the free online course, you will see it covers router setup too. You never mention the model number of AB PLC, but if it has the port, then it has in the software a place to change IP. There are all kinds of things IT persons can do, like use router to assign IP static or virtual, but with PLCs, the IP on PLC itself needs to be static. I like to keep it simple. I think after you go through the videos in the course, you will be able to figure it out.

[nadjim]

Thank you. I say "Should I add another ethernet card on this PLC so that it can have an address similar to the other two ?" because I can't change the IP adresses of the PLCs they are static and used for others thinks. They are in different subnetwork.