I am able to do iPhone USB tethering under Ubuntu which will be recognized as eth1 interface (I also have an eth0 internet connection).
What I want to do is, when the eth1 is up, I want to make it be the default gateway, and if eth1 is down, then return back to using eth0 as default gateway.
How can I make it happen? I want solutions for both Windows and Ubuntu.
[EDIT] A compromised solution under Ubuntu is that I can set one of my interfaces as "Use this connection only for resources on its network" with the networkmanager. (Under selected connection-> IPv4 ->"Routes")