Using TIA Portal v16 Upd6, I have set up a project with an S7-1200 (6ES7214-1AG40-0XB0) PLC and WinCC Unified (PC station). Initially, communication between the runtime and PLC was flawless when connected directly via Ethernet cable. However, upon relocating the PLC to a distant spot, connectivity issues arose. Despite both devices being on the same subnet, the runtime displayed an exclamation mark on IO fields, indicating a lack of connection to the PLC. An intriguing workaround was discovered: reconnecting the PLC directly to the PC temporarily resolved the issue. Subsequently, reconnecting them via the network also restored proper functionality. This cycle had to be repeated each time the PC's IP address changed or upon a reboot. It is puzzling why this process is necessary and how to establish consistent communication without the initial direct connection step. Both Ethernet ports are within the same subnet, with correct TCPIP settings on the PG/PC interface. What could be causing this intermittent connectivity problem, and how can it be resolved for seamless operation without the need for repetitive direct connections?
Update: The issue has been identified and resolved. The PG/PC interface was originally configured as "TCPIP.Auto.1", but changing it to "TCPIP.1" has resolved the issue and everything is now functioning correctly.
TCPIP.Auto automatically assigns an IP address within the same subnet as the device it is communicating with. This feature proves to be extremely beneficial when connecting to multiple PLCs, as it eliminates the need to manually change your IP address for each one. However, while this function streamlines the process, it also restricts the ability to implement Routing/NAT and can cause headaches for IT departments.
Indeed, it is advisable to steer clear of using the '.auto' option for setting up TCPIP. When using TCPIP.Auto, the IP address is automatically assigned within the same subnet as the device it is communicating with. However, this can cause issues with Routing/NAT and lead to headaches for IT departments. It seems that opting for the .auto option may result in additional complexities. As suggested by aamirawan91, having ports in the same subnet eliminates the need for routing. This has been a common occurrence, especially among colleagues new to TIA, who select the .auto option without realizing the complications it may cause in getting online.
It's possible that there are additional enchanting elements beyond what I've already mentioned - that's just the tip of the iceberg as far as my knowledge goes.
It sounds like you have an interesting issue on your hands. This intermittent connectivity issue might be caused by a variety of factors but it appears to be tied to the fully established connections on your PC's IP address. I'd suggest checking whether the IP configuration stays consistent after reboots or changes, as changes in this configuration would necessitate a reconnection. In addition, ensure that your network infrastructure (switches, routers, etc.) supports Industrial Ethernet communication requirements since standard office equipment might not be suitable. Lastly, you could also consider utilizing static IP addresses for your PLC and runtime environment to prevent disconnects due to DHCP IP address changes. As a troubleshooting test, you could try pinging the PLC from the PC when the connection is down, just to see if it's a network issue or something unique to the TIA Portal connection. If this doesn't help resolve the issue, you might need to contact Siemens support for advanced troubleshooting.
Considering the symptoms you've described, it seems like the issue might be related to ARP (Address Resolution Protocol) caching. Once the PLC and PC are directly connected, they can remember each other's MAC addresses, which facilitates communication through the network afterward. However, this memory doesn't persist through an IP change or a reboot, which explains why you need to connect them directly again each time. An ARP static entry might help resolve this issue. This would entail configuring the PLC and the PC to always associate the other's IP address with its corresponding MAC address, thereby maintaining the connection consistently. Kindly refer to your device manuals or seek professional assistance to make these configurations correctly.
It sounds like you've already done a fair bit of troubleshooting, so I'm going to throw a wild card in here. It looks like your PLC could be getting blocked by a network device like a firewall after the devices are initially separated. The direct initial connection can bypass some filters and make the PLC 'known' and trusted to the network infrastructure, but this trust may be removed or reset under some conditions - like a changing IP or a reboot. So, it's not about the Ethernet settings but more about the network security settings. Maybe you should try to add a static IP for the PLC and allow it through the network firewall. Please check your network architecture and security settings in detail.
It sounds like a frustrating issue! It might be worth checking if there are any IP address conflicts or DHCP settings causing the PC to get a new IP each time it reboots. Sometimes, network devices can struggle with routing tables when an IP address changes unexpectedly. Also, ensure that the Ethernet switch or any networking hardware in between is functioning correctly and is configured properly. You might also want to look into using static IPs for both your PLC and PC to avoid these changes altogether. If the problem persists, checking the communication parameters in TIA Portal and potentially updating firmware on your devices could help as well. Good luck!
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Answer: Answer: Relocating the PLC to a distant spot can lead to connectivity issues, even if both devices are on the same subnet. This can result in an exclamation mark on IO fields, indicating a lack of connection to the PLC.
Answer: Answer: A workaround involves temporarily reconnecting the PLC directly to the PC, which can resolve the issue. Subsequently, reconnecting them via the network can restore proper functionality. However, this cycle might need to be repeated each time the PC's IP address changes or upon a reboot.
Answer: Answer: To establish consistent communication without the need for repetitive direct connections, ensure that both Ethernet ports are within the same subnet and have correct TCPIP settings on the PG/PC interface. Troubleshoot any issues related to network configuration or IP address changes to maintain seamless operation.
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