How do I make my Macs use Thunderbolt Bridge instead of Ethernet or WiFi for file sharing?

[Adora]

Hi,

can someone help me please?

I read several instructions and still don't understand how a Thunderbolt Bridge works. In every instruction it always looks like it works automatically without changing anything in the settings. Just create one on both sides activate file sharing and connect network in Finder.

It's an M4 Pro mini and an M3 iMac. So I used a Thunderbolt 4 cable to connect them.

I see each Mac name listed in the System Information of the other Mac in the Thunderbolt section with 40 Gb/s, so they are definately connected via Thunderbolt.

File Sharing is activated on both sides and both have a name M3.local and M4.local.

I am able to connect them in Finder via Network from both sides.

The indicator is always yellow. Shouldn't it be green?

When I remove the bridge or cable everything is the same. They seem to share data over the Router where both are connected via Ethernet or even (directly?) over WiFi when it's enabled. How do I know what is used for data transfer?

The speed is very slow. It definately never used Thunderbolt, whatever I tried.

When I got my M2 Pro MacBook Pro. I set the damaged 2017 MBP in Target Disk Mode and used a Thunderbolt 3 cable to connect both and copying was blazing fast. But I want a permanent connection between two Macs that are both usable normally while copying over files.

What am I doing wrong?

 

[chabig]

Do these instructions help?

Use IP over Thunderbolt to connect Mac computers

Connect two Mac computers together using Thunderbolt and set them up to communicate with each other using Internet Protocol (IP).

support.apple.com

Please post a picture of your Network Settings.

 

[Adora]

Do these instructions help?

Use IP over Thunderbolt to connect Mac computers

Connect two Mac computers together using Thunderbolt and set them up to communicate with each other using Internet Protocol (IP).

support.apple.com

Please post a picture of your Network Settings.

Hi, thanks for trying to help. I knew that site and wasn't sure what exactly to post also I just deleted both bridges when I read it yesterday.

I now did a little more research again. The connection was ready on both Macs and I found the solution, Ethernet is always preferred if connected.

(I found it here: https://forums.macrumors.com/thread...ing-for-internet-between-two-m1-macs.2388249/)

When I removed the cables from the router everything was much faster when copying files from one to the other Mac but not as fast a from a Mac in Thunderbolt Disk Mode and I also found out why too.

Since no Ethernet is no solution for me. I'd rather copy the files on an external TB4 SSD and connect it to the other Mac. This is faster even if everything has to be copied twice.

The TB bridge normally only supports 10Gbps max. or somehow up to 20Gbps when it's using the latest USB 4 version instead of TB, what someone found out, when he connected his PC, that also had a Thunderbolt 4 port. This seems to be the absolute limit because of duplex, he got about 17Gbps.


I'll just tried what that bsdguru posted in the thread from above:

https://forums.macrumors.com/threads/problem-solved-help-configuring-thunderbolt-sharing-for-internet-between-two-m1-macs.2388249/post-32790216

I tried to connect with ifconfig in Terminal what seemed to work somehow but it only worked with sudo, that's why in the other thread there was an error.

When I only type ifconfig I see both active connections and both Macs are indeed connected via Thunderbolt, although ping is giving errors. But the problem stays the same. Ethernet must be disconnected.

en3: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
    options=460<TSO4,TSO6,CHANNEL_IO>
    ether 36:31:55:5c:99:04
    inet 17.1.1.1 netmask 0xffffff00 broadcast 17.1.1.255
    media: autoselect <full-duplex>
    status: active

en2: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
    options=460<TSO4,TSO6,CHANNEL_IO>
    ether 36:e9:31:12:e6:00
    inet 17.1.1.2 netmask 0xffffff00 broadcast 17.1.1.255
    media: autoselect <full-duplex>
    status: activep

As permanent solution creating a service just for Thunderbolt 1, 2 or 3 simply instead of using the bridge doesn't do anything. Nothing happens when clicking on it only Bridge works.

Strangly the Mini has two other options, I used one with this 17.1.1.1 IP and even got a green connection without entering anything else. But that was red soon after I did whatever and never went green again, also not when created new.

I wanted to do the same on the iMac with the other 17.1.1.2 IP but the option is just not there and the others don't work only bridge is working for creating a new Thunderbolt service.

This was just a try, if it might changed anything. But it only killed my continuity features somehow. At least i can't just use the mice and keyboards on both Macs anymore and just drag something over on the other Desktop.

Maybe another reboot will fix this.

For now I have enough of Thunderbolt connections betweeen two Macs.

 

[chabig]

I appreciate the above post. I’m “helping” based on my Mac knowledge, but I don’t have any similar setup so I can’t test anything. I can only throw out ideas. I assume you are aware that the network interfaces are used in order from top to bottom, and that you can drag them into any order you want. I wonder what would happen if you put the Thunderbolt bridge at the top of the list. It might then be primary for Mac to Mac file transfers, while Internet access would be taken care of by a lower interface such as WiFi or Ethernet.

 

[Adora]

I appreciate the above post. I’m “helping” based on my Mac knowledge, but I don’t have any similar setup so I can’t test anything. I can only throw out ideas. I assume you are aware that the network interfaces are used in order from top to bottom, and that you can drag them into any order you want. I wonder what would happen if you put the Thunderbolt bridge at the top of the list. It might then be primary for Mac to Mac file transfers, while Internet access would be taken care of by a lower interface such as WiFi or Ethernet.

Thanks I didn't know that. I didn't know anything about Networks until I wanted to try that Thunderbold Bridge. I didn't even know I can just establish a Network connection between two Macs with two clicks in Finder, when both are via Ethernet and maybe also just WiFi on the same Router. Then I just did a little research.

I had disabled WiFi and Bluetooth before and turned it on again recently because of Universal Control.

I could drag anything in Network Settings, then I found what you wrote it in the three dots, somehow I never saw that option before.

But out there everything stayed the same:

Nothing changed. I tried copying a 5GB file and the speed is max. 100MB per second, what indicates a 1Gbps connection.

Maybe that order is only relevant for Internet connections.

I then did a reboot but it did not change the order too. In Terminal those en numbers for the Ethernet ports/connections also did not change. It's still en3 on the mini and en2 on the iMac.
Ethernet is en0 and WiFi en1.

When I use a real TB Bridge instead that manual Terminal connection I also see no IP I could ping, there is just a MAC address. The reason ping produced errors yesterday was by the way just because the Firewall is set to not allow it.

I also don't know if there is a difference if I use my Apple ID or the other Macs username for a Network connection. It always automatically takes the Apple ID and I have to disconnect to take the username. But this doesn't change anything noticeably anyway.


Sadly I have another problem since yesterday I removed a Thunderbolt Dock from my iMac because it blocked both TB4 ports and I wanted to test if it changes something when the bridge does not go through a Dock first, but that didn't change anything. I also changed the position of the iMac a little on the desk while doing this.

Since then Universal Control doesn't work anymore. I really tried everything I found, also connected the Dock again and even put the mini on the iMacs foot what should be more than near enough, but distance seems not to be the problem. I tried several positions.

It was interrupted once when I put those manual IPs in Terminal yesterday. I confused it with Continuity/Handoff in my last post, but Handoff is needed anyway too for Universal Control and Continuity is the name for all features together, that icloudes more than one device, like universal clipboard for example too.

But it worked again after a reboot and all I entered manually in Terminal was gone.

I could use both mice and keyboards on both Macs and just drag files on the other one's Desktop or anywhere else in Finder. And this is all just not working anymore now and I just don't know why. But Screen Mirroring is no problem from the iMac to the Mini. Connecting an iPad as extended display also is no problem.

I turned it on and off and rebooted, logged in and out on both Macs from iCloud used two Terminal comments to delete cache files and whatever I could find a solution like using Sidecar with an iPad, what all helped others.

 

[Adora]

I appreciate the above post. I’m “helping” based on my Mac knowledge, but I don’t have any similar setup so I can’t test anything. I can only throw out ideas. I assume you are aware that the network interfaces are used in order from top to bottom, and that you can drag them into any order you want. I wonder what would happen if you put the Thunderbolt bridge at the top of the list. It might then be primary for Mac to Mac file transfers, while Internet access would be taken care of by a lower interface such as WiFi or Ethernet.

I just found out, the new order only affects the services that are offline. And also found out that this Thunderbolt Ethernet becomes active when I use the Ethernet port of my Dock. I just wonder why there are always two and I can create a new service with those when I delete both.

My other TB4 Dock that even uses two connections on the iMac is just displayed as USB LAN:

Now ALL TB ports on both Macs are greyed out and in use for Thunderbolt Bridge when I click on new service and it seems there were just two Dock on the mini had been there twice because it was connected to another port before. But I had always two to choose for creating new services before I deleted both.

Those now greyed out before were just useless, when clicked, simply nothing happened.