Comment 17 for bug 1056437

I would like to take a shot at completing this mini feature.
If I understand this right, this is a way for l3agent to pass off L3NAT & routing to external network to an external router/network created by the provider. Is this understanding correct?

If my understanding is right, I would like to take a look at what needs to be done. I understand that this has to be done maintaining backward compatibility.