Q: I have a small home network set up using a NetGear wireless router to connect my computers to my DSL modem and give me a firewall. I recently created an FTP site (thanks for the excellent guide by the way), but I cannot seem to access it from outside my network. I think that my router is causing the problem, since this seems like the most logical problem area, and I know it has a hardware firewall. I'm still using the default router settings, so I'm guessing there is something I need to change to allow access from outside the firewall. Any ideas?

A: Yes. Most routers use a NAT (Network Address Translation) firewall, which stops all unsolicited data from entering the network. When a computer inside the network requests information from the Internet, the firewall records the IP address of the computer and that of the Internet location it is sending data to in a table. When data comes back from the Internet, the router compares the IP address of the source to the table and if data had been requested from that address previously, it is allowed into the network and sent to the requesting computer.

Obviously, with this type of firewall, no one is going to be able to get at your FTP site from outside. They can type in your IP address with an FTP client, but as soon as the request hits the firewall it will be dropped. What you need to do is create a virtual server. A virtual server is a set of specific instructions for your firewall, telling it that if x kind of data is received from outside the network on y port, it should be allowed into the network and forwarded to z machine, in your case, the FTP server.

Any home router that contains a firewall should have a screen for setting up virtual servers. Consult the documentation if you have trouble finding it. You will need to set up a virtual server for TCP port 21 pointing to the IP address of your FTP server. This should resolve your problem.