I have an FTP site that is only accessed via a large private WAN that interconnects most of the hospitals and clinics in our area. We now have a client in Alaska (I'm in Washington) that is not on this private WAN, but I need to give them access to our FTP site without making it completely public. Site to Site VPN is not an option, nor is a client based VPN unless there is a way to have it always on.
I have the outside ip address of their gateway, so I am wondering if I can assign my FTP site an outside ip address that can only be accessed by their gateway ip address, and maybe put it on some obscure port. Is this possible? Thanks!