Issue with Profinet Communication
Hi everyone,
I am experiencing an issue with a Profinet/BACnet gateway.
I have a small network consisting of:
- A PC with IP 172.27.62.113 running Yabe
- A PLCnext with IP 192.168.1.10
- A Profinet/BACnet gateway with IP 172.27.62.108 on the BACnet side and 192.168.1.35 on the Profinet side
According to my tests, as long as the PLC is not connected to the network, Yabe can see the gateway and its variables. However, as soon as I connect the PLC, the BACnet communication drops, and there is no Profinet communication. This observation is supported by network analysis using Wireshark. I have attached the analysis file for reference.
From what I have analyzed, after connecting the PLCnext to the network, it sends a Profinet DCP identify multicast request in packet #250, followed by an ARP request in packet #251. After these events, BACnet communication drops, and the gateway only sends LLD-type packets.
I have tested this multiple times and always get the same behavior.
The gateway configuration is correct. The Profinet diagnostics on the PLCnext web server indicate a status of "ok" and "connected," but with a warning 0x0020 Bit 5: "Neighborhood information is not available."
I conducted tests with this same gateway and a Siemens S7-1200, and the communication worked fine, so the gateway itself does not appear to be faulty.
I have also tried upgrading the PLC's firmware to versions 2024 and 2023, but it still runs on 2021.0.3 LTS (21.0.3.35554).
Thanks for your help!
I hope this clarifies the situation. I look forward to your insights and solutions.
Thank you!
Comments
Regarding the firmware update, please note this information in the Info Center:
Just a wild guess but do you use a switch having port mirroring enabled (or a hub) when you try to capture the network traffic?
I assume the Profinet communication doesn't drop, in fact it's quite the opposite. The PLC and device start communication with each other and you won't see that because the switch doesn't send the packets to the port the PC is connected to (except for multicasts).
As for your tests with the S7, did you use identical Profinet communication settings (reduction ratio, updates times etc)?
Cheers
DivisionByZero
Hi DivisionByZero,
Thank you for your response and suggestions.
No, I don't have a switch with port mirroring. I am currently using a basic 5-port switch or I connect the devices directly. Without a switch with port mirroring, how can I verify the communication on the Profinet side? More importantly, why is the communication on the BACnet side dropping?
Regarding the Profinet configuration, it is quite basic; I only set the IP and device name, and I don't touch the other parameters. I will review the configuration to ensure I haven't missed anything.
I appreciate any additional advice you can provide on how to effectively monitor Profinet traffic with my current setup and how to troubleshoot the issue with BACnet communication.
Cheers,
Reluz
Hi Martin,
Regarding the firmware update, please note that I followed the instructions as per the information in the Info Center, but the firmware is not updating. I have attached images for your reference.
Thank you for your assistance.
Best regards,
Reluz
Unfortunately it's not possible to update the firmware on an AXC F 2152 using a raucb file for an AXC F 1152.
Please try a raucb file for the AXC F 2152.
Profinet communication:
I'd say when the webpage shows it's up and running you can assume that it works. Another way would be to connect the gateway's process data (e.g. PN_AR_VALID) to a variable in PLCnext Engineer and view the online value.
Monitor network traffic:
Sadly I'm no Linux expert but maybe it's possible to log incoming traffic on the PLC's network card similar to what you do with wireshark on your PC.
BACnet communication:
I don't know the first thing about BACnet. Sorry.
Is your PC directly connected to the BACnet side of the gateway or is everything connected to the same switch? Does it make a difference if the switch is only connected to the Profinet stuff? Does it make a difference if the switch is only connected to the BACnet stuff?
Related to logging traffic directly on a PLCnext Control device, the Linux utility tcpdump can be used for this purpose:
Knowledge Base Link: How to use tcpdump on a PLCnext Control