X20CP3485 IP address on IF3 (running as ethernet) not set after power on

I have an X20CP3485 where IF3 is set as an ethernet interface with manually set IP address.
Since the last changes to the software (settings of IF3 have not been changed) I have the problem, that after powering on the plc is not reachable with this IP address (no ping response, no online communication). After a warmstart (via Automation Studio connected to IF2, or via SYSreset in the application) communication over IF3 with the configured IP address is possible. Any ideas what could be the reason, that the IP address is not set after power on?
Greetings and thanks for any replies

Hi, if the problem is related to the last change I would personally revert this part of the code/configuration to check that the last change is really the cause of the issue. If so, would be interesting to know what contains this sw change. In the meantime you can check the connection to the plc using sdm, interesting would be CPU load and logger. If you would like more help from us, share with us some printscreen (IF3 settings, sw change, logger, sdm info,…).

No, I’m pretty sure, that there is no relation to the last changes. Only possible, that some newer frimware files have also been transferred. The curious thing is, that after power on the plc is not reachable on the Powerlink IF (set as ethernet), but after a warmstart it is! Unfortunately the machine is onsite and I have no access to it. At the moment I make a warmstart with the SYSreset function when an input is set. So the user has to set the input after powering on and then after the performed warmstart everything runs fine. If nobody has an idea, I woud try to automate this routine for the user. So, is there a possibility, to detect, if the plc is booting after power on or after a warmstart?

Without knowing your project and your changes it is hard to assume. I would personally compare projects and check what are differences…

To your question I think SysInfo can help you detect it. B&R Online Help


some time ago I thought, I’ve a similar issue, but in the end it was only a bad cable that not had a 100% reliable contact (in my case at the switches side). But for me it looked like that it always happened at boot. But that’s a different story, I don’t think that’s the same at your site.

I don’t think you have noticable entries in the logger directly and only after power fail (also warnings could be interesting), right?

For the following questions: I know that you’re remote connected only, but maybe someone is on-site who can have a look?

  • It would be very interesting to know, if a layer 1 link was detected after power on or not - so, if the PLK led and / or the LED of the communication partner connected to IF3 (for example a switch) are “on” or “off”.

  • And, does it happen on every power fail (even if the power fail only lasts some seconds), or only if the machine was switched off for some longer time?

  • By the way, is the communication partner of IF3.ETH also switched off when PLC is powered off? And does the behavior change if only the PLC is powered off?

  • And last but not least, does the IF3.ETH interface doing some active communication (like “ping a different device”, or “sending data via TCP client to a server”…), or is “passive only” (only server’s like ANSL server is running)?

Why I’m asking this is: I’ve seen in very, very rare cases in the past some interference with network interfaces and switches (independent of if it was a PLK interface running as ETH or not), for example when both are powered on and booting at the same time, and the ETH interfaces do some resets while booting (X20 PLC do that).

I’ve also seen in very rare cases issues with some switches, when a ETH interface does not send any outgoing data actively after a power on and before the switch had finished his own boot (in that case, the switch never “learned” the MAC address of the PLCs interface, and as long as no MAC broadcast was send to the PLCs interface, the switch “never knew that the PLC is here”).

As I said, these have been definitely very rare cases in very special combinations and they all happened in correlation with ethernet infrastructure devices like switches or routers, nevertheless I wanted to mention them.

Best regards!

Thank you for your answer. To your questions, I can only tell, that it happens after every power off and the interface is passive only. Unfortunately I even haven’t a remote connection. The machine is onsite and running for years. Nothing to the infrastructure has changed. I only tansferred some changes to the code. No system settings have been changed, no hardware was added or removed. So I think, only possibility is, that some newer firmware files from a hardware update also have been transferred and now make these troubles. As I already mentioned above when I’m next on site, I will automate the Sysreset, so that is performed after every power on. The machine has been working now for more than 15 years. Maybe there’s also a hardware problem. Who knows?

Hi @istech! Do you have any updates on this topic?

No, unfortunately not.