Configure NIC as dedicated VPN interface

Question

I have a setup with two ethernet connections. I'm trying to configure it so that one of the interfaces (eth1) is configured for use with OpenVPN and is not a default route for anything. (Connections to the VPN interface would be controlled by manually selecting it on the application level.)

Its also important that the setup not interfere with incoming traffic on the non-VPN interface (i.e. remote ssh connections, etc).

Anyone know how to set up such an environment?

(My system is running Ubuntu 15.10.)

Answer 1

First upgrade from 15.04. It's dead and vulnerable to attack.

Secondly, I'd strongly recommend doing this with in an LXC container (or with Docker, which uses LXC). A container limits anything within it to whatever you like, including network stuff.

That way you can force OpenVPN onto a certain network interface. And then force a load of applications to use the VPN. All without disrupting the main network connection and everything outside the container. For granular access, you can run a proxy within the container and expose that to your host computer's applications.

It isn't trivial though. Currently it involves using privileged containers (okay but not ideal) and there are several hacks you have to do to make it all work. The most complete guide on the matter is here but an amount of Googling around "lxc vpn" will help.