I have one public IP and three linux servers behind a linksys router. What I am needing is to have port 21 forwarded to each server behind the router. I have setup something similar for HTTP. One of the three servers acts as a primary and accepts everything from port 80, then determines the destination from the domain name. I need something similar for FTP. I would switch ports but my ISP will only allow port 21 to be open for FTP. I can assign a domain specifically for FTP if I have to so thats not a problem. I just need to have my FTP login viewed from a domain level not an IP it seems. Can it be done? I have searched around the web but have not found much on this. If somebody has any suggestions or can refer me to somewhere please do. I am not quite a noobie but I am no expert when it comes to linux and am in need of some help

what you really need is three public IP's, or a VPN. You could also set ssh to run on 21 and use it to forward ports.

First, 3 public IP addresses are out of the question. Second I have never setup a VPN. And third, I have never seen how to forward ports using ssh and how would I use ssh to access the server instead of telnet?

first thing: google is your friend
second thing: there are many howto's for forwaring ports via ssh, you can find then on google
vpns aren't particualrly easy, but can be used.

It might be helpful to let us know what you're trying to do with this setup exactly.

A buddy and I have a development web servers that sit at my place on my Internet connection. My buddy lives in a different state and connects back to the development server to upload and test web sites/scripts before going live. I have a guy who lives in a different town that needs to upload work. We have multiple servers because we have different production servers we are emulating. One of us uses apache 1.3 with php4 and one has one with php5 and then we have a php5 with apache 2. I have setup the http to direct the request to the correct server using apache but my ISP will only open up port 21 for my ftp. So I need to be able to access one of three servers to upload content depending on who is logging in and for which server.

You're definitely going to need to set up a vpn. what sort of client OS's ar eyou using?

Windows XP Pro and Windows 2000

http://poptop.sourceforge.net/ is the linux vpn server for windows clients, you can probably tweak it to name things based on username, or hostname.