Troubleshooting Your Ethernet or Thunderbolt Connection in Luna Display

If your Thunderbolt or Ethernet cable isn’t connecting the Luna apps, there are a few things to check. The Thunderbolt or Ethernet connection must be established between your devices before launching Luna.

The Thunderbolt or Ethernet cable must be plugged in before opening Luna. Please allow up to 60 seconds for devices to recognize the connection before launching Luna.

Changing the Connection Filter

Luna should automatically connect if it detects an active Ethernet or Thunderbolt connection. If not, adjust Luna’s settings to only connect over a cabled connection instead of Wi-Fi.

Note: While Thunderbolt works in PC-to-Mac mode, we recommend Ethernet when possible, as Thunderbolt is not always reliable with Windows. This is due to how Windows behaves with Thunderbolt cables.

Mac-to-Mac:

In the top menu bar, click Luna Display > Settings. In the Mac-to-Mac tab, change "Allow any network interface (default)" to Connect via Ethernet only or Connect via Thunderbolt only.

PC-to-Mac:

On PC, click Luna Display > Preferences. In the Connectivity tab, change "Allow any network interface (default)" to Connect via Ethernet only or Connect via Thunderbolt only.

Check Thunderbolt or Ethernet Connection on macOS

The Thunderbolt or Ethernet Bridge is a network interface that allows data transfer between two devices via a Thunderbolt or Ethernet cable. This should be established once the cable is connected between the two devices. To check that the Thunderbolt or Ethernet Bridge has been properly set up:

Connect both devices with the cable.
Go to Apple Menu > System Settings > Network on both Macs.
Look for Thunderbolt Bridge or Ethernet / USB LAN in the left sidebar.
If connected, it will show a green or yellow dot labeled “Connected” or “Self-Assigned IP”.

If it says "Not Connected" (red dot):

Unplug and replug the cable securely.
Try a different cable.
In Network settings, select the connection and set IPv4 to "Using DHCP."
Remove the Thunderbolt or Ethernet Network from the list and re-add it.
Restart both devices.
Contact Apple Support if the issue continues.

If connected and Luna still won’t detect it, try a ping test below to check communication between devices.

More Ethernet Troubleshooting:

Make sure both ends of the Ethernet cable are fully connected to each Mac, router, or access point.
Restart both Macs, router, or modem.
Switch to a new network location in System Settings.

For more help, check out Apple's support article for troubleshooting an Ethernet connection on a Mac.

More Thunderbolt Troubleshooting:

Make sure both ends of the Thunderbolt cable are fully connected to each Mac, router, or access point.
Make sure the cable is Thunderbolt-certified.
Restart both Macs.

For more help, check out Apple's support article for troubleshooting a Thunderbolt connection on a Mac.

How to Complete a Ping Test

In Luna, set connection to Allow any network interface (default) under Settings > Mac-to-Mac.
Quit Luna on both devices.
In System Settings > Network on each Mac, confirm the connection says "Connected" or "Self-Assigned IP."
Note the IP addresses listed for Thunderbolt Bridge or USB Ethernet on each device.

To complete the ping test, open Terminal on your primary device (instructions to find this here: Open/Quit Terminal) and run (press Enter after entering this information to run the command):

ping [IP address of secondary Mac]

Next, open Terminal on your secondary device (instructions to find this here: Open/Quit Terminal) and run (press Enter after entering this information to run the command):

ping [IP address of primary Mac]

If the ping communication is successful, it will look similar to this ping test result:

If the ping communication is unsuccessful, it will look similar to this ping test result:

If the ping is unsuccessful, try again or reset the cable connection. If the ping works but Luna doesn’t connect, contact us for further help.

Using Adapters for Wired Connections

Adapters can be used with Thunderbolt or Ethernet cables if your devices have different ports. See our guide: Using USB, Ethernet, or Thunderbolt with Luna.

For example, to connect a 2015 iMac (Thunderbolt 2) and a 2021 MacBook Pro (Thunderbolt 4), you’ll need a Thunderbolt 3 to Thunderbolt 2 adapter with a Thunderbolt 2 cable.

Or, to connect the same devices using Ethernet, use an Ethernet to USB-C adapter for the MacBook Pro.

Please avoid plugging Luna hardware into adapters or docks. While we do not recommend plugging the Luna hardware unit into any adapters or docks, using an adapter or dock for your Ethernet or Thunderbolt cable should not affect your connection through Luna.