Odd Thunderbolt Ethernet problem

MacBook laptop with Thunderbolt ports. We got Apple Ethernet adapter. Configure it in the Network preferences for one location (as Thunderbolt-Ethernet). Works. Trying to configure it for another location. It shows red dot that there is no network connection. Nothing was changed except the location selection in the Network control panel. Going back to the other location config and it is green.

What gives?

What is the difference in configuration between the two locations?

Most ethernet connections are going to use DHCP and get all their addressing and other configuration details from the network, so you can leave it in that mode no matter which location you’re in.

I suspect you hard coded an IP address, router, DNS or somesuch, which is not available at your second location.



The colored blip next to the interface should be green even if the IP configuration is wrong afaik. It changes from green to red in the location with working thunderbolt ethernet if I unplug the cable (as expected) and back to green when I replug it. In the other location, it stays red (goes from green to red when switching locations). I refer to locations as in locations defined in the network control panel. Physically we do not move.

The story is as follows:
The user has location for wifi-based connections and by mistake created there the connection through the cable. Mac seems to default to wifi, so the user has to disable wifi manually through the wifi icon on the menubar (then enable it later). I wanted to create a new location specific for the cable-based work with wifi off. I have such a setup and it work just fine. It is a business location where all IP data is entered manually and each device is assigned a fixed IP address. There is also wifi at that location but it serves a different purpose and does not give access to local services. The user has to use that wifi access occasionally as well.


Wifi default…
In Mac System Preferences/Network Settings you can change the order of the connections (use the settings icon at the foot of the window and select Set Service Order). You should be able to drag ethernet above wifi so that ethernet will be the first connection, if available.