I managed to connect to my reach unit using ethernet over usb as described in http://docs.emlid.com/reach/software-development/#connecting-to-reach-via-ssh.
I am wondering if it is possible to change the usb0 network ip (on the reach module) to something else. And also if it would be possible to configure it to connect to a gateway I have on the other side of the usb cable.
I tried looking for /etc/network/interfaces as I found other guides for Intel Edison. However, it seem that reach is running something slightly different and I was unable to find the relevant file.