A few weeks ago, I had to make one of the toughest choices I’ve had in a while: a 30” Dell display, or a 27” Apple Thunderbolt display. I went with the Thunderbolt display, partly because the colors are better, but mostly for the convenience of having USB and ethernet integrated into the display.

The way this works, you can just plug your USB peripherals and your network cord into the Thunderbolt display. Then, whenever you dock your MacBook Pro, you just connect the single Thunderbolt cable and the display, USB devices, and network all work magically.

It’s much more convenient than doing the daily morning dance of plugging four or five things into your MacBook, and it’s the closest thing we have to a good MacBook Pro dock.

Well, that’s the theory anyway. In reality, while the USB works fairly decently, the ethernet connection dropped out on day one, and I haven’t been able to get it back since. Until today.

Here are the final steps that worked for me. Hopefully somebody else can save a bit of time with this:

1. With the Thunderbolt display connected, visit the Network tab in System Preferences. If you see Display Ethernet and/or Display FireWire in the list of network interfaces, select each one and use the minus (-) button at the bottom of the list to remove it.

   For me, Display FireWire was listed, but Display Ethernet was not. I’ve heard of others having strange symptoms with neither or both listed.

2. Unplug the Thunderbolt display. This will not work if you keep the display plugged in while doing the next few steps. Trust me, I tried it.

3. sudo rm /Library/Preferences/SystemConfiguration/NetworkInterfaces.plist

4. Restart your MacBook Pro and log back in. Once you’ve logged in, connect your Thunderbolt display again.

5. Visit the Network tab in System Preferences again. If you see Display Ethernet and Display FireWire listed, you’re all good. Otherwise, click the plus (+) button at the bottom of the list of network interfaces.

   From the Interface dropdown, select the interface you have missing and click Create. If you have both interfaces missing like I did, you will have to repeat this step for the other interface.

After all that, everything seems to be working smoothly for me.