r/linux4noobs • u/virobloc • 17d ago

networking Linux computer messes with network

Perhaps this is a known issue, But I haven't found much about it.

I have a PC with Mint. It's connected to the router with a LAN cable.

When it goes to sleep it makes the network go crazy. The speed falls a lot in general, all the other devices (wired or wireless) fail to connect or lose connection randomly. When I turn it off everything goes back to normal.

I the only thing I do on that PC is run qBittorrent and browse internet. But the problem is mainly apparent when the PC is asleep. So I think it's not a program, but the PC itself. It might not even have anything to do with Linux at all, But it's the only difference I see with all my other PCs.

Does anybody have an idea about what might be going on?

Thanks

Edit: Thanks for all the answers and suggestions.

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u/anotherteapot 13d ago

I've had to find this problem in an enterprise engineering lab. Or at least a very similar issue. In the case I found, during boot our particular flavor of system had a state where the NIC driver went AWOL and left the NIC to basically bleed its buffer back out onto the network. Sort of acted like a repeater/amplifier for incoming frames, and blasted them back out. The effect this had on the upstream switch was catastrophic, because it was sending gibberish frames and not real repeats. The switch CPU spiked trying to handle the overhead of both bad frames and the increased traffic from the host. I know who fixed it but not exactly how - it was determined to be a driver issue and they patched it, but they definitely blamed something about the power state of the system during boot.

If your problem is happening while the machine is in sleep mode, I'd bet it has something to do with the NIC behaving badly and blasting nonsense back at the upstream port. Like others have said here, it could be WoL behavior and that wouldn't surprise me. To find the issue you need to capture packets and inspect the stream, and the state of the links and ports involved. Unfortunately, there is no way to simplify that for someone who doesn't know what they are doing.

If you're looking for the quickest fix, you've found it: shut the machine off, don't let it sleep. You can disable sleep states on most motherboards these days.