Ethernet Card Not Being Detected On My iMac 20-inch Early 2008

Coincidentally I've just started having this problem, too. Last night all was ok and I turned by Mac off before hitting the bed; this morning the built-in NIC is no longer detected and I have the exact symptoms you have.

A few extras:

1) I have boot camp, and the NIC still works perfectly when booted into Windows

2) I use a powerline adapter, and the light indicates the cable is plugged in; as soon as I unplug the end from my mac, it goes out

3) I did SMC and PRAM reset to no avail

4) I booted into diagnostics and all was ok; I carried on to the bit where you can browse the support site, and it worked even with wifi disabled, so clearly it was going off my wired connection

5) I booted into recovery and had the same experience as in point 4 - the nic was working perfectly

So all this seems to point to something being off on the OS itself.

Looks like this may be down to a stealth security update pushed out that's broken the BCM5701 driver. It's discussed here: https://www.reddit.com/r/apple/comments/47tfos/warning_software_update_03151913_ breaks_ethernet/

I was considering trying to roll back the exclusion, but it sounds like a bit of a pain, frankly, so I think I'll just hold fire for the weekend and use wifi and hope it gets fixed by Monday.

I had the same problem at it was the silent security update 031-51913 for sure. I just downloaded and installed OS X again and it solved the problem. Maybe not the fastest solution but a very easy one.

Definitely a long way! Hopefully they've disabled the update so you don't get it pushed again.

For those that have a recent Time Machine backup, you can restore the /System/Library/Extensions/AppleKextExcludeList.kext file mentioned in the link I added in my earlier thread by:

1. Boot into recovery mode (Cmd-R)
2. Disable system integrity (open terminal from recovery and enter csrutil disable)
3. Reboot into Mac OS
4. Restore the file from the previous time machine backup (the bad file was dated a day or so ago, the version in my recent time machine backup was dated back in December; you can browse to the /System folder by pressing Shift-Cmd-G and entering the path)
5. Enable system integrity (open terminal from recovery and enter csrutil enable)
6. Reboot into Mac OS

I am also having the same problem on my Macbook Pro 13inch early 2015, my Thunderbolt Ethernet adapter stopped working.

Same problem here, on iMac 27", early 2013. I called Apple Support. They advised me to reinstall (data was kept). No luck. Second advise: restore from time machine to last backup of Feb 26th. Im reluctant to do this, as it will take time (again) and then, will the problem stay away? Will use Wifi for the time being.

And yes, this Mac has the BCM5701:

Apple support just stated (via e-mail) that it is likely being solved in a future update. They will contact me if so.

The same at my late 2013 iMac... Ethernet connection not working the last hours. Ethernet card doesn't appear at system report! Totally unacceptable. Do something folks!

I can see that I had the "Incompatible Kernel Extension Configuration Data" install version 3.28.1 last night. I have a late 2009 27" iMac.

One thing that is strange on my Mac is that if I look for my Ethernet Cards nothing comes up. I am connected via WiFi right now but normally I don't have WiFi on and just connect using a LAN cable.

Per my second post, Apple pushed a bad update that mistakenly blacklisted the ethernet adapter. If you have a recent Time Machine backup from before a yesterday, you can restore the file by following the steps I highlight in my third post.

@Jarrad e.a. That (partly) solved my problem. Earlier this day I deleted the ethernet port from network setup. So after these steps I was able to re-add the ethernet port. Then I had to boot once again. Solved (however Apple should have solved it)!

Thanks APPLE ! What a PITA !!!!!!! 😠 Jarrad's post worked for me Thank You !

Nothing like spending the first two hours in the morning trying to figure out whats going on. Lots of coffee in hand , eyes wide shut lol , have a great day everybody

@Jarrad: Thanks a lot, I spend 3 hours this morning to figure out what happened! I restore the .kext file from yesterday, and my ethernet card is back!

Hello People,

what if i don't have an option to reset it with my time machine (because i simply didn't make a backup)!

1. Just wait for an update / fix from Apple ?

2. Will they notice the error ?