How to Connect to a PLC with an Unknown IP Address

Hi everyone! I’ve been asked this question a few times, so I figured I’d put it here.

NOTE: This is really only useful if you are using a controller without a C-FAST card. If you have an external card, just write your new project–known IP Address and all–via an Offline Installation.

Imagine you get your hands on a Compact-S or C-Panel PLC. You turn it on, eager to transfer the project you’ve been working on. You plug in your Ethernet cable, open up Automation Studio, try to search for it…and nothing shows up. Whoever used it last must have deactivated SNMP, and you don’t know the IP Address!

Fortunately, there’s a way to make your PLC discoverable again: put it into BOOT mode.

Typically, a PLC can be manually put into BOOT mode by pressing its reset button for less than 2 seconds, releasing it for less than 2 seconds, then pressing it holding it down again until the PLC enters BOOT mode. What BOOT mode looks like varies between different PLC families, so check your device’s data sheet to be sure.

  1. Once in BOOT mode, make sure the desired ethernet port on your computer is connected to the ETHERNET port on the Controller via an ethernet cable.

  2. In Automation Studio, go to Online → Settings…

  3. Make sure the “Browse” button is toggled ON

  4. You should see your PLC populate in the window, without an IP address set

  5. Right-click your PLC and select “Set IP Parameters”

  6. If you have IP parameters set up in your open project, you can click “Copy from project” to set them; or you can enter the desired IP address for the Controller manually.

  7. Click OK to close the Parameters dialog box.

  8. With the IP address set, right-click on your Controller and click “Connect”.

  9. In Automation Studio, you should see the current mode change from OFFLINE to something else in the bottom right corner or the screen, indicating that you are now connected.

Now you can transfer your project. Keep in mind that your project’s ethernet settings will overwrite whatever IP address you just set.

Happy automating! :robot:


Thanks for the nice description.
There are also educational online courses for users of the B&R solution. These are just a click away.

The course “Getting started: Introduction to Automation Studio, project creation and connection setup” describes, in addition to many helpful topics, how to establish a connection to the target system.

The contents are only visible when logged in . You can log in using the access data for the B&R website . B&R customers can obtain their access data from their B&R sales representative or use our Contact form.

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Good walkthrough, Blake.

A few additional notes regarding establishing a connection to a PLC.
• Starting with Automation Studio version v4.8, SNMP is default disabled on new and upgraded projects by default. It can be enabled by the application developer in the Ethernet configuration. SNMP is always enabled in BOOT mode.
• In order to connect to a PLC, a project needs to be open in Automation Studio. This project doesn’t need to match what is on the PLC. The PLC will still be browsable, but the connection action in step 8 above will not result in a PLC connection.
• If the IP address is “” then the PLC is configured to obtain an IP address automatically from a DHCP server. This is the default for BOOT mode.

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The needing to have a project open has caught me out MANY times.

Some information that might be worth adding:

In case of a strict firewall setting at your company, the correct protocol has to have an exeption made so that you are able to find a fresh PLC while using the “browse” command/button.
We had this problem in our company and it took quite some time to figure it out.


If you have a new PLC (without removable memory), e.g. C80, CP-0XX you have to:

  • Create a new project
  • Set all connection settings on the IF interface (configuration) (IP address, SubNetMask, etc.)
  • Enable SNMP (optional)
  • Set the Ethernet parameters (host name, gateway) in the CPU configuration. (optional)

Then you can generate a USB boot stick under the menu item:
Project-> Project installation-> Create USN Install Driver.

  • This must then be plugged into the IF1(USB1) on the panel and restarted.

ATTENTION: The update does not work on the USB2 because it is linked to the GPOS.