Ran into an issue where, after adding a network card, and adding a static route on a second network card, I was unable to connect. I could see Windows receive the SYN packet, but it made no attempt to send a SYN+ACK back.

The issue was that, when you add a route to windows like so:

route add -p mask

Which should send all traffic for towards, Windows will happily assign this route to a network card that cannot access

The solution is to find the MAC of the network card you want it to go out of (ipconfig /all), then run:

route print

And at the top there is an interface list. Look up the interface number there, and use this command, where 22 is the interface number:

route add -p mask IF 22