08/05/2026
Here is the revised business-account version, incorporating the image as part of the challenge:
Think you can diagnose this industrial Ethernet problem from the clues?
During FAT testing on a control panel today, our team encountered one of the most unusual network problems we have seen.
The PLC, laptop, managed Ethernet switch, and other devices initially communicated normally. After approximately 30–40 minutes, however, communication across the network became extremely intermittent.
For several minutes, most devices would be unreachable. Then, without warning, communication would return for roughly 20–30 seconds before disappearing again.
Our team investigated the usual suspects, including:
• Network addressing and configuration
• Cabling and physical connections
• Laptop and virtual-machine settings
• PLC diagnostics
• Switch configuration and port behavior
• Connected devices and possible network interference
Despite changing several variables, the symptoms remained remarkably consistent.
One observation eventually pointed us in the right direction: the switch appeared to be showing activity on a port that did not have a cable connected.
The accompanying photo was taken during the troubleshooting process. Everything needed to identify the problem is contained in this post and the image—but the most important clue is easy to overlook.
What do you think caused the intermittent network failure?
Take a close look before answering. We will reveal the cause in a follow-up post.
