USB Ethernet adapters randomly stop working on M1 MacBook Pro and macOS Big Sur

Same issue with Belkin F2CU040 adapter which seems to contain a RTL chip.

Connectivity gets lost in video calls. Had to switch back to WiFi as for now.

Looking forward to getting a fix in the future updates...

Your comment regarding video calls made me think. I have also noticed that the crash often happens in video calls. I did a lot of tests today and can confirm that the driver crashes reproducibly in every second MS Teams call.

I think i have exactly the same problem and i described it over there:

https://forums.macrumors.com/threads/ethernet-disruption-in-clamshell-mode.2277222/

I configured my router to limit the connection between my M1 MacBook Pro and the NAS from 1000 Mbit/s to 100 Mbit/s. At that speed the disruptions rarely occur and Time Machine Backups mostly work, but that's not a satisfying solution.

Having the exact same issue, with 3 types of dongle. Reconnecting t he network cable do show its sense the disconnection, but IP cannot be renews.

Disconnecting the dongle and reconnecting works, but then randomly goes away again.

I can see that both Adapters (HP, Goldtouch) are Realtek, but how can I see that model so I'll try new drivers ?

Apple Menu / About This Mac / System Report / Hardware / USB / 10/100/1000 LAN will show you the Product ID 8153. That's the Realtek 8153 that is apparently build into every USB-C Ethernet Adapter compatible with the M1.

There is no specific Realtek driver available for Big Sur that is working with the M1. The generic Apple driver AppleUserECM.dext seems to be inefficient, instable and most likely the cause of our problem: See https://www.reddit.com/r/mac/comments/gukh9c/fyi_usbc_hubs_with_ethernet_might_cause_high_cpu/ and https://gist.github.com/MadLittleMods/3005bb13f7e7178e1eaa9f054cc547b0.

Ethernet Adapters using Thunderbolt 3 instead of USB-C are not affected.

Based on that, this looks like a growing body of evidence that these adapters are not working in Big Sur, regardless of processor.

Best bet may be to try to apply pressure on the Vendors to get a new Driver for the 8153 chip.

I just want to add my experience. I purchased a MacBook Pro M1 so that I'm able to do video editing on the go. I also had the idea that I can use it to stream my gameplay from my gaming PC using OBS + NDI. Installation and setup went smooth however, when it came to broadcasting, anywhere from 5 mins. to 30 mins., the broadcast would stop. I did a lot to try and fix the problem from changing bitrates, changing encoders, swapping ethernet cables from Cat5e to Cat6, and also buying another USB-C hub (QGeeM branded). I started thinking maybe it's the computer I bought (refurbished model from Apple Store online). Anyway, I'm glad I came across this as there seems to be an issue with USB-C hubs or dongles with the Realtek device. Hopefully we can get a fix soon.

Cilusse wrote:

Just got a reply from Apple saying this issue is fixed in a future update.

If you are a dev you can already get it!

Not sure if 11.4 is that "future update", but since upgrading I have yet to see this happen, with Time Machine backups proceeding normally. Now that I've posted this, I'm sure it will break - but give the 11.4 update a shot! For what it's worth, the version on com.apple.DriverKit.AppleUserECM.dext hasn't changed; still at v1. Holding out hope that whatever code is responsible for this is elsewhere and has been updated.

Performance still isn't all that hot topping out at ~800Mbps (the same hub on my old Intel MacBook Pro gave a consistent 940Mbps) but I'll take stability any day. I hope this is indeed fixed, as I was dreading spending over $200 on a Thunderbolt hub just to get a working Ethernet connection. Wired performance - accept no substitutes.

While 11.4 made this much better - I made it at least a week as opposed to a couple times a day - the bug is still there. Woke up this morning to find the adapter in the same state as before with a hung Time Machine backup. Here's hoping that Apple can make a permanent fix.

I still have the problem on 11.4. It only seems to be an issue with videoconferencing apps for me. I can stream for hours on Stadia and GeForce Now, but I generally can't make it through a 1 hour meeting on Zoom or MS Teams without encountering the issue.

My recently purchased M1 Air has this same problem - I initially experienced it with a '11-in-1' multi-dongle, and assumed a simple fault in the dongle.

Regrettably the problem also occurs with a dedicated USB-C -> Gigabit single-purpose dongle. Both devices have Realtek chips and I have not installed any drivers; using whatever Big Sur 11.4 provides natively.

Did you resolve this problem or find the other chipsets (which?) work reliably? I don't want to spend £30 on a Belkin adapter if I can help it :)

Similar issue. I don't know about drivers and chipsets, but my 2019 MacBook Pro about 3-4 weeks ago started the same issue on Ethernet, I'm using a dock CalDigit TS3 Plus but also replicated issue through a CalDigit Mini Dock. Works fine on WiFi speeds but Ethernet kills the entire internet connection once it starts processing big files. I use a Dropbox finder app and constantly syncing large video files, and everything works fine until it starts syncing any large files 500mb+ maybe, not exactly sure on size. But I can switch the WiFi on and everything connects fine. Or I can unplug adapter, plug it back in, and get it working again until it starts downloading those files again....

I logged a case with Apple and even spoke to an engineer for 20 mins or so after getting through the front-line support scripts. The only change which has been made so far is to create a new 'Network Location' and switch to it. This is made the problem 'better' however it still drops out, even when using the overpriced Apple USB-C adapter (which is also RTL8139 based).

I've chased up the case but with no reply as yet. I'll try again now; thanks for the reminder.

I have the same issue: Belkin USB-C Ethernet Adapter, F2CU040 with pci id 0bda:8153 (Realtek Semiconductor Corp. Belkin USB-C LAN) randomly looses connection (repeatable after 300GB transferred via SCP to my local NAS) under macOS 11.4.

Apple Support couldn't help. I should try with a different user profile and booting in safe mode.

I should ask Belkin for a replacement (unsure why there is no replacement from Apple Online Store as a warranty from the dealer as EU consumer laws). Support couldn't recommend alternatives.