On Thu, Apr 03, 2025 at 09:38:29PM -0400, Jeffrey Walton wrote:
... when a cable from the server is connected to the Ethernet port of a client device, the Debian server will automatically recognize the new physical connection and then automatically activate that connection. It sounds like the client is connected directly to the server via ethernet, presumably without a cross-over ethernet cable. So both ethernet ports would need to auto-sense the configuration.
That hasn't really been a problem for 25 years, it's definitely not something to worry about on consumer gigabit hardware. (Auto-MDI-X came out around the year 2000 as an option on 10/100Mbps gear, and was more common on consumer grade hardware originally--professionals being presumed to know what cable to use. The earliest 1000baseT hardware was sometimes a bit flaky, but those issues were ironed out a long time ago and the simplest $5 realtek chip you can buy these days doesn't care whether you're using a straight through or crossover cable.)
As confirmation, the ip and ethool output show the link as up; if we were looking at some bizarre hardware which had MDI/-X issues there wouldn't be a link at all.