Thunderbolt bridge and File Transfer questions  



I have several related questions about connecting two macs via Thunderbolt bridge. Here is my scenario: I have a 2017 iMac Pro, and a 2018 15” MacBookPro (I know…brag, brag brag!). I purchased a 40GB/sec 0.5 meter cable from OWC which I leave plugged into the iMac. I activated the thunderbolt bridge (TB) Network interface in the Network Preference pane of both Mac. I turn on SMB file sharing on the iMac Pro.

Connecting the cable to the MacBook results (sometimes) in the activation of the TB interface (after 10-15 seconds) with a “self-assigned IP”.  I connect via smb://169.etc. File transfers are fast.  So far so good!

Question #1. Sometimes the TB interface is not activated. It seems the only way I can get it to activate is restart the iMac Pro (the sharing computer).   I’ve looked around to see if there is a way to re-activate the interface (which I imagine has crashed?) without a restart. Some discussion on stack exchange from 2014suggests “kextunload” and “kextload” on some appropriate interface files…but this does not seem to do it.

Does anyone have a suggestion for re-activating the TB interface without restarting?

Question #2. I have the TB interface set to do  “Using DHCP”. This is fine, but each restart gives a different IP address, which I then have to look-up before I can use smb to connect.  I tried giving the interface a fixed IP address “” say. But this doesn’t work.

Is there a way to fix the IP address for the TB interface?

Question #3. Should I plug the cable into the MacBook when it is closed (asleep?) or when it is awake? Should I remove the cable only when it is asleep (closed?)?  I worry about shocks to the interface that could fry something…but maybe that is silly.

Thanks for any suggestions!


Try creating a System Preferences -> Network -> Location and name it "Offline" (or anything you like).


Now for the "Offline" location delete every networking interface on the left.


When you select this location via the Apple menu -> Locations entry it will basically shutdown the networking stack and take your Mac offline.


Now switch back to your normal Networking Location (Automatic ?), and the network stack including your Thunderbolt interfaces should all re-initialize.


It is easy to try, and if you do not like it, you can always just delete the "Offline" location.

Thanks--nice idea. I've got this set-up and I'll see what happens when it next crashes.

Just to follow-up: I still haven't gotten the Thunderbolt Bridge interface to reliably activate. Most of the time it works, but, say 20% of the time it fails. The trick of an "offline" setting for the network interface doesn't seem to help. 

Rebooting does the trick, but is certainly not what I would call a "just works" mac-like experience!