I have a WL500g, connected to an Alcatel Speedtouch 500. Works fine, even my 128 MB USB-stick (Aldi-Medion) is available on the LAN via FTP. Then i desided to try to make the USB-stick approachable on the Internet (WAN) and the problems started.
It turned out that the Speedtouch modem is not just a modem but also a DHCP-server. Than means my Internet IP-adress is converted after passing the modem into a different adress. this way you can't approach the USB-stick.
to solve this problem you can "spoof" the Speedtouch modem. It becomes transparant for the ISP IP-adress; and simply passes it through to the WL500g. When you check this with IPCONFIG it looks oke. As long as i connect the modem directly to my computer everything works fine: Internet explorer, Outlook express, Kazaa: all oke.
When i connect the Speedtouch to the WL500g my computer says that there is an internet connection (icon in tray), but only Kazaa works!
I know this is a confusing story, because it has little to do with the original FTP-over-WAN-problem! But i have to solve this first before i can take the next step.
Please help and remember i'm not a Pro...