I have a Debian workstation with two interfaces: the ethernet jack attached to the motherboard (eth0), and a USB to ethernet adapter (eth6). eth0 connects to the internet, while eth6 connects to some special equipment only accessible over ethernet.
When the workstation starts, it connects to eth6 by default; when this happens the workstation cannot reach the internet and I must choose to connect to eth0 from the network manager. I would like it to connect to eth0 by default. How can I do this?