If anyone finds this topic here in July 2025, I was encountering the exact same issue with an M4 Max Mac Studio. High load would cause the Ethernet connection to drop and reconnect.
TL;DR: Solution was turning on Jumbo frames in macOS Ethernet settings.
What I did:
- Cycle all power: switches, routers, the works.
- Check all Ethernet connections of course, from the Studio all the way to my Fios ONT.
- Reset the Mac's network settings. Flipped from auto Ethernet config to manual, back again, all the usual software steps.
- Still having the issue. Hmm.
- Replaced a bunch of cables; one of my runs had some tight turns and was an older but previously working cable, but figured better safe than sorry. This was boiling the ocean but I had intended to replace some cables anyway, so figured why not do it as part of troubleshooting.
- Issue persists. Literally have never run into this problem before. Hmmmmm.
So I started running the amazing
Packet Loss Test and keeping an eye on all my gear. Over a long test (120sec) I visually caught my switch unlink (lights out!) the connection to the Studio. It would drop, macOS would signal that Ethernet was disconnected, and a second later it would relink.
Fiddled with the switch. Tried another patch cable. Still the same problem.
Went back to macOS Ethernet settings, into hardware. Reset some stuff. On a whim, left Jumbo frames turned on—somewhere in the recesses of my brain from my sysadmin days was "Jumbo packets are good on high bandwidth low latency networks," which describes mine.
Fired up Packet Loss test again. Fingers crossed. 120sec later, everything was fine. Ran the test again about 10 times in a row, eyeballing the switch and the test simultaneously.
Problem totally solved.
I can't explain this at all, but sure enough, this worked for me. Give it a shot if you're finding your Studio's Ethernet is being dramatic.