If you're having problems with your Mac's Ethernet port this morning, the culprit may be an errant automatic update that Apple published over the weekend. Luckily, the damage isn't permanent: an Apple support article posted yesterday will walk you through diagnosing and fixing the problem, which involves connecting to your network via Wi-Fi and running a software update command in the Terminal. If you're reading this and your Ethernet port is working fine, odds are good that you've already installed the follow-up update released to fix the problem.
Same problem on an iMac (21.5-inch, Late 2013) running El Capitan 10.11.3. I rebooted this morning and now my ethernet port isn't working, although the port seems alive, is detected by 'About' and shows connection lights on my router. Agree with comments that Apple software quality (control?) is falling, falling, falling. Perfect install first time with no flaws or scary delays, network and sound fixed (so yes, the RTL8192CU driver from ZyXEL does work on El Capitan, as you can see). Note that this trick ONLY works with Clover 3259 and above, and a CsrActiveConfig value of 0x03 allows unsigned kext’s but keeps the other security – you might want that.
El Capitan Os X Download
The culprit is an update for System Integrity Protection, the El Capitan feature that protects some system folders and keeps unsigned or incorrectly signed kernel extensions (or 'kexts,' roughly analogous to drivers in a Windows or Linux machine) from loading. In this case, the kext used to enable the Ethernet port on Macs was blacklisted—if you restarted your Mac after applying this update but before your computer had a chance to download the quickly issued fix, you'll find yourself without an Ethernet connection.
This blacklist isn't updated through the Mac App Store like purchased apps or OS X itself. Rather, it uses a silent auto-update mechanism that executes in the background even if you haven't enabled normal automatic updates. Apple uses a similar mechanism to update OS X's anti-malware blacklist, a rudimentary security feature introduced in 2011 following the high-profile Mac Defender malware infection and occasionally used to push other critical software updates.
Ethernet Driver El Capitan Free
Ethernet Driver El Capitan Mac
Why Apple blacklisted its own Ethernet kernel extension is anyone's guess; one theory suggests that the update may have been intended to go live after the release of OS X 10.11.4, which could include a newer patched kext. Whether it was an outright mistake or a well-intentioned update that was released too early, the end result is inconvenience for users.