I've used a lot of usb-based devices, and still do technically with a thunderbolt dock for like the past 5 years, and not really run into this on either ubuntu or arch. I've run into some weirdness before though with wired or wireless nics. Basic linux network 101 applies... test it like a network engineer, layer 1-7.

use "ip link" to see the state of of the physical nic, or verify layer 1

use "ip neighbor" to verify you see mac forwarding ala arp table, or layer 2/3

use "ip address" to verify exactly that, verifying dhcp or static configs take place for layer 3

use "iftop" or "tcpdump" to see what traffic is sending, and if any is coming back assuming your nic has link for layer 2-7

Aside from that probably a kernel/firmware thing. Use journalctl -xe or -b options to show you boot and logs (as root) of what happens around the events with your nic. It could be some firmware bug, realtek's used to be terrible cursed names, but really haven't a problem for me in the past 5-10 years I'd say, and you're hard pressed to find a usb nic that *isn't* a realtek.

You can probably rmmod and insmod the realtek driver too as long as something isn't using it. If it's busted, it should not be used, but stranger things happen, especially if firmware is hung in a funky way, which is usually what would always happen with them.

-mb

On Fri, Sep 23, 2022 at 12:04 PM T Zack Crawford via PLUG-discuss <plug-discuss@lists.phxlinux.org> wrote:

I am very interested in the answer because my desktop does the same thing if I tell it to hibernate, boot into my windows dual boot, and reboot back into linux. I can regain network access again by hibernating again and booting back into linux directly (no windows). Pretty annoying because it takes a solid 2-5 minutes to shut down when hibernating. At least it still does the job, just with delay.

This only happens if I try hibernating and then boot into windows (not full shutdown, not hibernate and boot directly to linux). It has always happened since I enabled hibernation (arch wiki instructions). Having Systemd restart NetworkManager does nothing. Setting up a new network configuration with networkmanager does not solve it. This is with my motherboard ethernet and my wireless USB adapter. I spent some good energy trying to figure it out, but never did.

Did you update kernels today? What if you downgrade?

Put the solution as a boot script. Or at least bash profile instead of run commands (otherwise it will run every time you spawn a terminal shell)

Sep 23, 2022 11:14:35 Jim via PLUG-discuss <plug-discuss@lists.phxlinux.org>:

> A few months ago my Dell Optiplex 7010 running Ubuntu 20.04 started booting up without the network. I'd reboot the machine and the network was there. If I shut down the machine and turned it on again, no network. I thought something was wrong with the built in ethernet adapter, so I bought a usb adapter, disabled the built in one and the problem went away until today. Now it's happening with the usb ethernet adapter. Rebooting the machine fixes the problem gets the network up and running. If I start with a cold boot and reboot at the grub screen, I get the network. I have 3 SSDs and 2 HDDs. I have the same video card that I had before this problem first showed itself. It's a GeForce GT 710.
>
> I looked online and found something telling of other people who have had this problem. They disconnected video cards and went back to the built in video (display port), and removed hard drives that had been added later and this fixed the problem. The ultimate solution was to replace the power supply. I disconnected one SSD and the 2 HDDs. I don't have anything that can use a display port, so I left the video card in place. All I had connected were 2 SSDs. One it boots from and my home directory is on the other. The problem still showed itself when I booted the machine, so I shut down and plugged in everything again. This thing has a 240 watt power supply. Do power supplies go band in such a way they don't produce the amount of power they used to?
>
> Any ideas what it might be? Is there a command that would tell the system to set up the network again? If there is, I could put it in the .bashrc until I get this fixed.
>
> Thanks
>
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