Thunderbolt ethernet does not connect when plugged in.

thanks Nueva york, did the trick

guys, its hard to believe apple would design something that does' t work. This adapter is gigabit ethernet right.

that means you better have at least a cat 6e cable for reliable connections. i've seen this many times at work.

what could be happening is when you plug your cable in if its connected to a gigabit switch it negotiates communication

speed. it only takes a couple of ethernet packets for both ends to say "yes i can comm at a gigabit". then if you have

a crummy cable (less than cat 6e) when you start communication on the web you are getting near end and far end

crosstalk. the computer is so busy asking for retransmits that you don't get any bandwidth. I see it at work all the time.

back you adapter off to 100mbit and if thats the problem it will start working.

Thanks for posting. Your suggestion fixed my problem. I appreciate it !

Similar/same problem: Ethernet-Thunderbolt dongle plugged into Macbook Pro. Home LAN going through two switches and a router to get to a cable modem. In "Network" a green dot displayed for the dongle, but there was an intermittent message indicating a (nonexistent) IP conflict. Also, ping failed. What worked for me was to turn off wireless, get rid of old locations, start a new one, and then go through building the connection. When that didn't work, the screen message was to restart my router. I restarted all switches, the router, and the cable modem (possibly overkill to do everything, but it was easy and it was a way to reset all devices)--and waited. After a couple of minutes the Ethernet/Thunderbird lashup made it all the way through the milestones, and the connection was finally good.

This problem and its close relatives have been noted in forums for some years. It appears that it is not terribly hardware-specific. It also doesn't seem to depend on the version of OS X (at least within the past few years)., and may not be triggered by firmware or driver updates.

hwi brian.. same problem here. I have a MBP Retina 15. very simple fix. In network preferences add new connection and select Ethernet thunderbolt. hit apply.

afterwards turn off wifi and like magic, ethernet will connect.

Gabriel

Thanks for all the suggestions! I was able to resolve this problem by entering Recovery Mode, turning off WiFi, testing that the Thunderbolt to Gigabit Ethernet Adapter was working in Recovery Mode, then selecting the Recovery Mode option for re-installing OS X. My Mac was back working in under 45 minutes, with all settings and files intact. Except now with wired ethernet working properly. Details below. Kudos to AppleCare phone support!

What didn't work for me::

I had first tried the solutions offered in this thread and in similar threads. None helped significantly. The only thing that had helped at all was deleting files from /Library/Preferences/SystemConfiguration -- sometimes deleting just NetworkInterfaces.plist, sometimes all files except com.apple.Boot.plist -- and restarting. Unfortunately, this solution worked only briefly, for one (sometimes two) plug-ins of the adapter. After that, the the Network pane reverted to not noticing the Thunderbolt-to-Ethernet adapter at all, even though one could see (via dmesg) IOThunderboltSwitch messages for each physical plug/unplug event. If I wanted to use wired ethernet, I would have to delete the files again and restart the machine. This process worked reliably, but it is not something you want to do several times a day as you move around an office, attend meetings, etc.

My system/network:

I have Mac OS X 10.11.3 installed on a mid-2014 Retina 15" PowerBook. The Thunderbolt-to-Ethernet problem started around when I upgraded to 10.11.3, or possibly when I upgraded to 10.11.2 . I use wired ethernet pretty normally: I plug in an Apple Thunderbolt to Gigabit Ethernet Adapter directly into my MacBook Pro, and plug a standard ethernet cable -- a cat 5e/RJ45 cable which works fine at gigabit speed with other laptops -- into the adapter. The ethernet cable plugs into a simple unmanaged gigabit switch, which is plugged into the building network. I tried multiple genuine-Apple Thunderbolt to Gigabit Ethernet Adapters; all showed the same problem.

What worked for me:

1. Back up your Mac with Time Machine (just in case).

2. Shut down your Mac.

3. Unplug Thunderbolt-to-Ethernet adapter.

3. Enter Recovery Mode: hold down cmd-r, press power button,

don't let go of cmd-r until you see Apple logo and a progress bar.

4. Turn off Wi-Fi: use icon and pull-down menu in upper right of screen).

5. Test internet connectivity: Select "Get Help Online". Once in Safari, enter the address of a website or two (apple.com, nyt.com) and see if they load and if links can be followed..

6. Select "Reinstall Mac OS X". Be prepared to wait a bit, this took me 45 minutes, and that is with the usual SSD in my Retina Macbook and a very fast near-Gigabit internet connection in my office, although I don't know if much network was used.

7. Log in and plug in Thunderbolt-to-Ethernet adapter. Check Network preference pane to see if all is well. Try an unplug/wait-a-few-seconds/plug-in cycle. Try another one. With luck: rejoice!

I imagine the OS reinstall would take longer on Macs with spinning hard disk instead of SSD.

Hope this helps!

Whoops! You'l need to insert:

Step 4a. Plug in Thunderbolt-to-Ethernet adapter.

Heh, the instructions are not much use without that step...

This fixed one of my 4 laptops with the same issue. I even went to Genius bar and they been so genius that they told me that the issue is local to my 4 laptops. Genius help!

Clicking "Advanced" -> "Renew DHCP Lease" solved my problems as well.

JediMindTrick's advice worked for me! For some reason after I deleted it from the Network pane, the connection was recognized as Bluetooth PAN. I had to reset the service order and hit apply and now it works fine again.

Hello,

An update: upgrading to macOS Sierra 10.12 completely fixed this problem for me.

Details:

Every solution in this discussion turned out to either not work or work only temporarily for my OS X 10.11 MacBook Pro. Since I last posted, I received more suggestions from Apple tech support. One Apple tech even kept in contact for a while and had me transfer over lots of diagnostic files to Apple, but no suggested solution ever worked for OS X 10.11 . Clearly a software problem: I could always find Thunderbolt Ethernet in Recovery mode, but Thunderbolt Ethernet almost never worked after normal startup, despite log messages indicating awareness of every plug/unplug, as described in my earlier posts in this discussion.

But: since I upgraded to macOS Sierra 10.12 weeks back (currently running macOS 10.12.1) , all has been fine. Not a single problem with the Thunderbolt to Ethernet adaptor. It connects to network seconds after plug in, every time. Hooray!