Disconnected Ethernet adapter never reconnects

Final note.

I just bought the OWC 10G Thunderbolt3 adapter. I can report that this adapter works as expected with connections and disconnections.

I never solved the problem with USB-C based Ethernet adapters. They will not recognize a disconnection/reconnection unless you remove the adapter from the preferences.

So this is a workaround. I do hope that some other version of MacOS solves the issue at some point.

Thanks

Improvement...

So I went into NetworkInterfaces.plist and preferences.plist and cleaned things up...

• removed several interfaces that were old and did not know where they were from
• removed en12 which was the currently working interface
• saved everything and rebooted

What happened?

USB-C dongle gets discovered and get and IP. All working.

If I unplug the device, and plug it back in, the device never reconnects, however, if I remove the device in System Preferences, disconnect and reconnect, the network comes alive again. So I no longer need to reboot. But there is no "hot plug" behaviour.

So marginally better. It would appear that something else is happening in the OS that causes the card to never return alive, unless you remove the driver and reinsert the dongle.

I'll keep on fiddling.

Thanks

Hi Chris,

Thanks for the suggestions. Unfortunately, all this was tried way before. The problem is very easy to reproduce.

1) Everything is working just fine.

2) Unplug the USB-C adapter

3) Wait 10 seconds

4) Plug the USB-C adapter again

5) Ethernet never comes back

6) Leave the USB-C adapter plugged in, and restart the Mac through the Apple menu

7) Once restarted. everything works fine.

So it's not cabling, adapter, ISP, or anything else. You can reproduce this with all the Apple adapters, AXxxx adapter, generic USB adapter, etc. This problem is really inside Catalina or Mojave (started happening with Mojave, the latest updates for sure - i cannot say exactly which revision - might have also been with High Sierra but that I cannot verify).

Thanks

Thanks Alex.

No changes.

1 added issue: if I remove an adapter in networking menu and tell MacOS to keep it for next time, that actually breaks System Preferences. From that point on, you must force quit Sys Prefs or restart.

What I am really looking for is a way to remove some of the adapters in that list permanently. I am aware that a number of additional adapters are in the list and need to exist for VPN, VMs, and so on. Currently, en12 is my ethernet adapter. So one of the scripts in the backend is definitely failing. Because as soon as you hit the apply button, the IP stack is never restarted properly. Unless you reboot the Mac. Even applied the latest update for Catalina a few days ago. No change.

I really appreciate you guys trying to help. However, the problem is really within one of the config files where the adapters are stored and the scripts used to bring them backup after a change. It's not the adapters, the ISP, the network, the Mac. This happened to my previous MacBook pro too.

Does anyone know which config files and how the scripts work to restart the IP stack?

(As a point of reference, I have been doing networking since AppleTalk, 10B2, before Ethernet was Ethernet, and even the actual Xerox network over Coax. I have been programming over IP for 30 years. So it's not my first rodeo. MacOS has been the most stable OS for several years now to the point where we always had a contest in the office: how long has you PC been up, and mine was routinely 60-90 days without a reboot. Alas, I have rebooted 9 times since 8am today and countless times yesterday. Not a happy camper.)

Again, thank for all your help.