Thats a valid point. The thing is I cannot think of a feasable method to handle it completely bulletproof. You cannot know who is going to make a connection to which IP out there. Also you would have to inspect all NIC's routing tables and subnets to know which interface is going to handle which IP packet.

Also I think having an unconnected NIC (no cable) and a not fully started NIC is ambiguous.

So any suggestions? I am open for good ideas of course.