You will have a physical Ethernet-port in a MBP (it is software-device: "en0"); You probably have an AirPort Wi-Fi in your MBP (it is usually software-device: "en1") ; Teathering can involve software-device on your MPB: "en2" . You may find limited, if not non-existant controls for managing "en2".
![:(]( "Sad")
