iis ftp 500 invalid port command

im running windows 2003, iis ftp server on port 21, and I set this computer as the DMZ host in my router.

I can log in just fine but when I try to perform an ls, dir, or get command it gives me the 500 invalid port command error and disconnects. At first it looked like it was a passive mode problem, but setting to DMZ host should have fixed that. D-Link router by the way.

***edit
Everything works perfectly across the internal LAN. These problems are only when the client is coming from the internet.
***

Any suggestions?

did u open both the 20 and 21 port for in and out going? on both UDP and TCP? on the router

FTP only uses TCP, not UDP. Before I set the server computer as DMZ host, i had 20/21 forwarded to it and 1024/1030 (for passive connections). But now that it's the DMZ host, this means that ALL ports go to it.

I was hoping for some kind of advice about how to restrict which ports IIS uses for passive FTP, or maybe if someone has had specific trouble with my router type for some reason. It's very odd that even as DMZ host it still gets this type of problem.

I think now that it might be my ISP who's blocking the port for me. like so many ISP's are blocking port 25 to in an "attempt" to stop/slow down mail born virii.

has anyone had this happen to them before?

i know that FTP only uses the TCP frame but with D-Link routers if you dont open the UDP you some time have problems with TCP aswell best way is to open both then use software to block the other

or at least with the 9 D-link routers ive had opening UDP on them when tring to use TCP for FTP connections and other transfering techniques has fixed the problem

updated the firmware on my router. works now.