I'm trying to use a steam link to connect and play games over the internet via vpn. Is it possible to port forward though a vpn. Most modern routers have PPTP passthrough which I rely on to connect to my VPN on networks I can't control. Here's a diagram with what I'm trying to do.
If you control the router who receive the valid internet IP address then you can port forward it, on that router, to any IP destination.
Example: If your VPN receives the IP (example only) 184.108.40.206 then the router/host who dial this VPN and receive this IP can port forward.
I recommend activating UPnP, it will let programs/games/software automatically forward some ports.
Example Skype and some games.