How to change the MPI node address for a Siemens S7-300 PLC

I have seven Siemens S7-300 PLCs connected to each other using the MPI (Multipoint Interface) interface. Siemens PLCs use the Siemens MPI protocol to communicate with external devices. I want to change the name of each of the seven PLCs. Here are the steps to accomplish that task.

First, connect your MPI cable to the first PLC. I will connect my laptop to each PLC individually. Power on the PLC and open Simatic Manager. The “New Project” wizard window will open. Just click Cancel to close the window. Now click on the Accessible Nodes icon on the toolbar. A window will open showing the identification of the PLC to which it is connected. My window shows MPI = 2 (directly). Make a note of this address and close the window.

Next we need to download a hardware configuration to the PLC. This is where we will change the name of the PLC node address. There are probably a couple of different ways to do this – here’s how I accomplish this. All seven of my PLCs are the same model; therefore I am using the same hardware configuration. For the obvious reasons, I want to give each one a different MPI node address. I have a project file that contains the seven programs for my PLC and a hardware configuration file. I open the hardware configuration file, and then double-click Hardware in the window on the right. This will open the HW Config window. In this window you should see your PLC with its given MPI address.

Remember when we clicked on the Accessible Nodes icon and saw MPI = 2 (directly)? My hardware configuration window shows an MPI address of 7. Place your mouse cursor on 7 and double click. Your CPU Properties window will open. It should open to the General tab. Look down and you will see MPI Interface Type with an address of 7. Click Properties and the MPI Interface Properties window will open. Using the dropdown menu, choose your MPI node address and make sure MPI (1) 187.5kbps is highlighted and click OK. You are now back in the CPU Properties window, where you will see that its address has changed. Click OK and you will be returned to the Hardware window where you can verify that your MPI node address has changed.

Now click on the Save and Build icon and then click on the download icon. The Select Target Module window will open. Click OK and the Select Node Address window will open. Here you will see the MPI node address that you assigned earlier. You will need to click the View button just below this. You will see the address of the current node appear, it should be the same one you saw earlier when you clicked on the Accessible Nodes icon. Just click on this number and you will see it appear in the MPI address slot under Enter Destination Station Connection. Click OK and the Download to Module window will open. Click OK and the Stop Target Modules window will open. Click OK and “Do you want to start the module?” the window will open. Click Yes.

Now go back to the SIMATIC Manager window and click on the accessible nodes icon. You will see your new MPI node address. You can view this same article with images at

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