Need Help Setting Up An FTP Server

I have 5 computers connected to a Linksys Etherfast 3116 Switch connected to a SpeedStream DSL Router. Also, I am using Bulletproof FTP server software to try and set this all up. As for IPs, the IP of all 5 computers is obviously seen to the outside world as the same one given dynamically by our DSL service, and internally all run on 192.168.254.10*, where * is the computer number that it is on, being 1, 2, 3, 4, or 5. Basically, how do I need to configure this all to have the server work? My guess was that I would need to set port forwarding in the DSL router for port 21 over to the one computer running Bulletproof FTP, 192.168.254.105, and then in Bulletproof somehow run Passive IP, but quite frankly I'm confused on how to do this all! Any help you can provide would be greatly appreciated, thanks!

-Rob

Does your modem have an option called IP Passthrough? That isn't the safest way to do it if you don't have a router but works. Also some modems have options to forward ports... not sure what your speedstream offers...

What i would do is this:

Let all traffic through modem
Configure router to deny ports except for the ones necessary to let through

I am not sure if your switch offers some sort of port forwarding, seeing as I am not familiar with any of the devices you listed, save the speedstream, which I utterly hate.