Ethernet keeps disconnecting

It's not a WAN issue. It's an industrial firewall that my company owns which is connected to a Cisco router provided by our ISP for a business-class Internet connection. I've spent hours between back and forth emails and phone calls with the paid support team we have for our firewall, if it was disconnecting they certainly would have picked that up right away and, frankly, I would have too.

Yesterday I ran a ping test to verify whether the VLAN (which is LAN-side not WAN-side) disconnects reported by Unifi were actually affecting anything. They aren't. I let the ping run for an hour or so (over 3000 packets) none dropped and the highest latency spikes were only +10ms and there were only 2 or 3 out of the entire 3000 packets sent, the rest of the replies came in within 1ms of each other. I suspect that the Unifi controller is reporting this inaccurately because our firewall isn't a Unifi product and is seen by the switch and controller as just another client device.

Was the usual connection reproducible? We noticed no issues when connecting a device directly to Ethernet. It is when there is a dock involved. That's when we get Ethernet issues.

Does your ethernet issue happen at home, in an office, or both?

I suggest that you try bypassing the docking station and plug the Ethernet adapter straight into your laptop. I'm not sure that it will help but since this seems like it's related to docking stations, it just might help, and it would be a good thing to test either way.

The simple thing you can do is to look at the router logs and wan status. If the router is connected to the internet and not having an issue with the wan connection as router logs can state (causing temporary loss which can cause other issues on the side) then you need to check router with computer or if its at the computer.

If its at the router then that has to be solved by configuration, factory reset, cables, or replacement. Routers are more complicated than ever and can do some really weird and unexpected things. For instance, one setting can majorly chop down internet speed (NAT Acceleration) and yet you still have internet or one setting could cause connection issues with one computer and all others may be fine (eg Preamble Type, firewall, ipv6, bugs from automatic firmware updates (or manual), etc). Other unrelated issues can cause unexpected side issues with connections.

If its at the computer then it has to be solved by narrowing down to networking hardware, driver, or cables. Some drivers like Intel have a whole lot of known issues. Hopefully the driver readme states known issues, etc.

If the computer is losing ethernet connection with the router then the router should state something if you're not seeing anything in Event Viewer for instance. Trying other hardware helps to narrow down things otherwise.

Hope that helps. If I had the exact issue, you'd have a fix but I'm not having ethernet disconnects. Didn't have any with Windows 10 or 11. WAN disconnects I was having recently but that's router side and out and appears to be fixed now :)