I recently attached a thunderbolt ethernet adaptor to my Mac, it is connect to a closed network that I am using for NFS sharing temporarily. My internet access comes through the WiFi. I have full internet access when I have WiFi only enabled, but as soon as I turn on the Ethernet, it stops working. It is clear why: My laptop is routing all internet requests through the ethernet connector despite the fact that that network has no external connectivity. I have no idea how to fix this. Any thoughts? ---------- Silly me, all I had to do was run Network Diagnostics and explicitly set the wifi as being the internet connection device and it worked.