Ethernet port on your Mac just died? Here's why

27 February 2016, 06:32

UPDATE: This has now been fixed by Apple. See this post for details. Original post below.

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Many thanks to Redditor zorinlynx who points out that a recent faulty software update pushed out by Apple breaks the Ethernet (network) port on some Macs.

The update is called “031-51913 Incompatible Kernel Extension Configuration Data 3.28.1” and has now been pulled by Apple, so there’s no longer any risk of updating to it accidentally – although zorinlynx suggests holding fire on any updates until word comes through from Apple as to what happened.

There’s no simple fix if your Mac’s been affected, other than to restore from a Time Machine backup taken before the update was applied. Downloading a copy of the driver file won’t work because it won’t be correctly digitally signed for your Mac. It’s possible to codesign the driver manually but doing so is somewhat complicated.

The update blacklists the BCM5701 kernel module driver for the Ethernet port and zorinlynx speculates that the update might’ve been an internal testing release that somehow escaped into the wild. The update should only affect Macs using Broadcom BCM5701 hardware. This can be discovered by opening System Information (hold down Option and click the Apple menu icon) and clicking the Network heading, then looking at the right of the window.

According to the Reddit thread, the list of affected Macs includes:

• iMac (21.5-inch, Late 2013)
• iMac (27-inch, Retina)
• Macbook Pro (13-inch, Retina, mid-2014)
• Macbook Pro (early 2015)

• Reddit: WARNING: Software update #031-51913 breaks Ethernet port on most Macs (BCM5701 driver)

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