Dropping Ethernet Connection on Big Sur

Try disabling WiFi as a test. If the problem continues, turn on WiFi and unplug your Ethernet cable. That's a starting point.

Keep us posted.

The watchdog launch daemon thingy has kept me safe from the en0 going dead for a month and a half now.

https://discussions.apple.com/thread/252189073?answerId=255005730022#255005730022

I had the same problem with my 2020 27' iMac ever since I upgraded to Big Sur.

However it has been good now ever since I did the following change:

Go to "Network" setup and create a new "location" for the internet.

Go to "Energy Saver" setup and only tick the following options:

Hope it can help your iMac as well.

Apple really should look into this issue ASAP. It is very annoying and frustrating for users...

@Adiaryofneed:

Within your long output of "ifconfig -a" you have many "en" interfaces.

en1, en2, en3, en4 are shunt together within the bridge group "bridge0".

en5 looks like an Ethernet interface, is up, but doesn't get an IPv4 address.

en7 looks like an Ethernet interface too, is up too, does get an IP adress but which is sign of failure at the DHCP level.

en0 doesn't look like an Ethernet interface, is up too, and does get an IP address which looks like the valid one : 192.168.1.211.

Your Mac have much too many interfaces up to make a serious diagnosis on it. I don't say this is the problem of Big Sur,

I just want to make clear no one can try to improve analysis of a problem with 8 interfaces looking potential Ethernet interfaces which are up at the same time. ( This would be an easy work for an Internet core router, but not for a home

computer which has a serious bug around the Ethernet software ).

Which one is the Ethernet interface with the actual problem?

Which one is the Wi-Fi interface?

I wanted to give an update on this issue which I originally posted nearly four months ago. I've been in touch with Apple Support regarding this several time. What I've learned: 1) My ethernet connection on this laptop is via USB. It is the same connection during the time it was working fine with Mojave. 2) When I check the Network screen it shows USB as the active top item on the left and states "Connected." This is when I have internet. 3) When I shut the Mac down and restart it, the top active item in the Network screen is "Bluetooth Pan" and I have no internet. 4) When I pull the ethernet cable out of the Mac, reinsert it and reload the web page I have internet and the top active item in the Network screen turns to USB. 5) This pattern persists regularly. So, the problem appears to be that the USB setting does not remain when the machine is turned off. 6) Apple walked me through so many test options I've lost track. One was resetting the P-Ram. Another was reinstalling the software. All to no avail. 7) The only thing that appeared to work was starting up the Mac in Safe Mode. 8) On a regular basis as long as I don't shut the Mac down, there is no problem. 9) One Senior Advisor said that this forum should be monitored by Apple engineers so they should be aware of the issue. The advisor said he would alert Apple engineers nevertheless. 10) In the meantime, Apple Support treats this issue as an isolated issue with my machine rather than a wider set of related issues experienced by users of this forum.

I hope this update may shed more light on this persisting issue for those of us still enduring this anomaly. I'm curious with other users, is this a USB connection issue? Are you also seeing the changes detailed above in the Network screen? Is your ethernet issue with Big Sur the same as I've described or different? Thanks!

Interesting development, though it's likely too early to throw a party. I'd created Ethernet only and WiFi Only locations configuration settings in the Network Settings display and for the last 38+ hours have been on WiFi only after a restart (not and shutdown and reboot) and when I had the Ethernet and WiFi location configuration, WiFi would drop after several hours and not allow me to turn it back on and activate it. So there appears to be some sort of prohibition in BigSur about running both Ethernet and WiFi at the same time on my Mac mini (late 2014).

I hope that any Apple engineers monitoring can use this information as useful in the correction of this problem. :)

Well, I'm going out on a limb today and installing BS 11.3 and crossing my fingers that the wifi issue when both wifi and ethernet are used has been resolved magically. The short blurb on the install didn't mention but then maybe our cries for help were heard but just not acknowledged. :)

Well, Big Sur 11.3.1 doesn't appear to have fixed it, I did! I had some Energy Saver features turned on for my Mac mini for some reason and I unchecked them all and restarted. That was 48 hours, 16 minutes ago and is the longest that WiFi has held while Ethernet is also active. Yeah me!! For the laptop folks, I think you all are probably going to need to scream louder to be heard.

I've encountered this problem on MBP 16" since upgrading to Big Sur. When I switch between wifi and ethernet (i.e., when I take my laptop away from my desk to work somewhere else, and returning to my desk, or heading out to work at a cafe), I would get this "No internet connection" issue

To fix this, I just need to open my router page (depending on your gateway address, mine is 192.168.1.254) then the internet comes back. Weird, but it works all the time.

I was also struggling with my network connection dropping after a few seconds. Reading about some people fixing it with removal of their VPN stuff, so I tried some settings on my VPN Tracker 365 installation. Didn't change that much, but after reconnecting the usb device, the connection stays up.

It seems that it has something to do with disabling "auto test when connecting in new network locations" or "auto test on startup or network change" on the tab "connection checker".

The problem in my case was solved many months ago with the Thunderbolt CalDigit TS3 Plus (plus I ranked Wired above Wi-Fi in network preferences; iPhone unlock still works if you do this

[Edited by Moderator]

We have the same problem in my company here. We bought a M1 mini and right out of the box it had the same problems. This bug even kills our whole Network if a machine with Big Sur runs for 1-2 days. We are running 12 Machines on Catalina without any problem! We recently also bough two 24" M1 iMacs which also had the same problem of losing the Ethernet connection after a short time.

I found a workaround for the new iMacs by setting the frame size in the Ethernet hardware settings to Jumbo frames. It seems to work but, of course, that's wrong as the MTU in the network is 1500 and not 9000. This at least works several days and without a restart but also it crashes the complete network after some days.

This all shows, that even the newest M1 Macs still have this bug out of the box without any additional Software installed. It really seems to be a software bug in Big Sur. All machines run the latest version 11.5.1.

Apple, this system is not an early Alpha or Beta. It has been out for more than half a year now. It is extremely urgent that you finally sort this out and correct this error. We all don't have the time to spend hours on the phone with your experts telling us to do all the basic things we, of course, already have done to solve the problem. We work with Macs since more than 20 years and we really know what we are doing. Here definitely is something wrong and I really ask you, Apple, to finally see this big problem that renders all Macs with Big Sur useless when operated in a professional business environment. All machines worked fine and stable with Catalina! We never had such a crazy bug within the last 20 years!

Regards

Stephan

Same problem.

Big Sur disconnects WiFi and Ethernet but says in the settings that it is still connected.

Rebooting the router brings WiFi back.

Unplugging and plugging the Ethernet cable back in also brings it back.

But projects that are uploading have failed because of this problem.

I have the same problem on a MBP 13 2017, running Big Sur 11.2.1.

I have both an ethernet (1 Gb) and WiFi running. When in calls (Webex, Teams, Zoom) or running streams (Youtube, Netflix), the ethernet cx freezes a couple of times per day. When I unplug the ethernet cable, the streams continue after a few seconds. I can then plug my network cable, and have a running ethernet cx again. Never had the issue before Big Sur.

Same issue. 2019 MacBook Pro 15" running Big Sur 11.2.1.

I also thought it could be something on my wired connection, but have moved to other wired connections and same result.

This all appears to have started with the introduction of Big Sur.