OSX 10.6.8 upgrade disactivated my ethernet port.

hi, here also 'cable unplugged' since the OSX 10.6.8 upgrade

(MacBookPro6,1, Intel Core i7, 2,66 GHz, 8GB memory, SSD disk)

following the advice from krpan also solved it for me,

only I did even simpler: i.e. without first removing or changing the ethernet interface.

I just rebooted once in safe mode by pressing the shitf key during boot.

Then started up the "system preferences.app' which took several minutes to launch.

This by itself brought my ethernet interface back to normal.

Then I shut down and rebooted in the normal way and

Now my RJ45 interface works OK as before :

no more 'cable unplugged'.

Hope this works for others too.

I had the same problem. As per the last suggestion, I went into safe mode and opened system preferences in hopes that it would correct itself. It did not.

Then I just restarted to go back into normal mode but was stuck in safe mode ! So I shut down, and unplugged the computer for 30 seconds. Rebooting resulted in my ethernet working again.

I imagine the shut down and power unplug is what did it for me, but who knows for sure.

I think it makes sense that just booting into the Safe Mode is sufficient (for those that it does work), rather then going thorugh all the rigamarole I went through and suggested in my previous post.

When Mac is booted in Safe Mode the kernel extension cache is ignored and dynamic loader shared cache is deleted. In addition, only required kernel extensions are loaded (e.g. no third party extensions get loaded).

I speculate that this "cleaner" enviroment allows the Ethernet card to be properly "reset" (firmware reloaded?).

Now, it could be that this procedure only helps users whose lack of Ethernet after 1.5.8 update is due to screwed up MAC address? Or it could be that it only works with certain Ethernet cards...

Mmmm... I dont think that certain Ethernet cards are the problem, cause I have the exact same Ethernet you have (built-in Broadcom 5764), and rebooting in Safe Mode didn't do anything.

Also, I'm noticing that at this moment, and in 10.6.7, that rare MAC address is back! I don't have any problems with the ethernet now, but is very strange. And scary...

Darn it, it is like Voodoo trying to get that problem fixed... I guess it's time mix some more potions 😟

The fake MAC address is disconcerting. And as long it was/is happening to a single Mac on the LAN it did not cause an issue prior to 10.6.8 update. I for one did not notice the fact that MAC address was screwed up until after the said update...

Note: I see that I said 1.5.8 in previous post, when I meant 10.6.8

I have exactly the same problem with my ethernet port on my 27-inch iMac after the "upgrade" to 10.6.8

I have a novel work around - I am using my ethernet to USB adapter that I bought for my Macbook Air - didn't have much use for it until now!

Works are treat and will keep me going until I try some of other fixes here...

This problem is giving me the absolute poo's!

Sometimes the safe boot technique works, and then a couple of days later, I have to do it again as the ethernet network is giving me the same error again. I re-boot into safe mode and it fixes it, but it's only lasting a few days. Damnation to intermittant problems!

Can anyone tell me how to reinstall MacOS? I tried running the program from the DVD, but the computer hangs, and doesn't continue the install. I end up looking at a grey screen with the apple logo for hours.

John

@krpan:

Thanks a lot for your post.It worked for me.

I've described my problem in another post: https://discussions.apple.com/thread/3140230?answerId=15518127022#15518127022

But after I tried your workaround with starting in safe mode the problem is nearly fixed.

The Problem:

No ethernet after 10.6.7 update. But AirPort worked. So I switched to wireless.

I thought Lion would solve the problem, but it did not. Still same problem.

The Solution for me:

Starting in safe mode.

Now I'm able to add the ethernet option as connection which wasn't there until now.

BUT:

The added "Ethernet" functionallity (cable LAN) is now labeled on the left side as: "AirPort" and the Wireless is now labeled as "Wi-Fi". It looks confusing, but the functionallity is there.

Perhaps someone knows how to fix this "labeling-problem".

Greetz

10.6.8 killed my ethernet also. I have two iMacs same model. One works fine the other doesn't. The one that doesn't work didn't get fixed by the other things either. I had to reinstall from the disc and that worked. So I did another update (consolidated 10.6.8 1.2Gigs) and now it doesn't work again. So there is something for sure in 10.6.8 that kills the ethernet.

Frustrated for sure! How do I contact apple since I'm past the date for warranty? This is there problem.

Has anyone tried this on OS X Lion?

Just another person saying I have this problem on my iMac7,1 core2due 4GB 250GB HDD running Lion 10.7

It is a big problem as my iMac is in a corporate LAN which is MAC address locked. My iMac throws out the fake MAC 00:00:04:00:00 which the CISCO switch then kills.

I still think my problem happened with the Lion upgrade which I made from a 10.6.8 (initial release) , as the corporate kill-switch was only stopping once 10.7 was in. My 10.6.8 on the iMac was working seemingly OK.

ifconfig shows the 'correct' eth0 MAC, but the actual packets that my iMac produces have 00:00:04:00:00.

My Bootcamp XP SP3 works perfectly with the correct eth0 MAC , once my kind IT department have reset their CISCO switch, I haven't yet tried any of the diagnostics or safeboot repairs. I still have permissions issue of 'fetching...' instead of 'Staff' due to being a Tiger username upgrade.

This is awful. We need an ethernet fix. My iMac at work, which is the same as at home, is working fine, but mine at home doesn't work at all except on wireless.

I have tried all the standard stuff of booting and resetting pram and other stuff.

My ethernet details are not showing up either in system profiler though they are on the computer that his working.

I'm running 10.7 Lion now.

But Lion does not fix the issue by itself!

In my case Lion takes over the problem which was caused by the 10.6.8 bug. I have installed Lion via Mac App Store: no clean install from scratch.

My Solution in Lion: safe mode; described in last post

Greetz

I erased the drive twice and started (make sure nothing was affecting it from the drive) over and everytime I updated to 10.6.8 it would break the ethernet. The third time I tried and booted from the CD (like the other 2) it wouldn't even recognize that I had ethernet in the system profiler. I've decided to buy a cheap USB to Ethernet adapter and forget it. I've wasted too much time on it.

The built in eithernet still doesn't work unless I boot from the DVD

I purchased a Kensington USB Ethernet adapter with a built in 3 port USB hub and it works great. It also includes a power adapter if I need to use it with a USB harddrive. I plugged it into the iMac and within a minute it was working just fine.

Conclusion: There was a change in the ethernet driver or the ethernet is damaged inside the iMac. It still doesn't make sense, it appears to work fine from the boot DVD.