external ftp

[crownfield]

In trying to do this,I keep getting partial answers, so..
what are the necessary and sufficient conditions to permit external ftp access to a 210?

My external ip address is correct and known.
the linkstation has the right local ip and gateway addresses.
port 9000 is forwarded to the linkstation.
ports 20 and 21 are forwarded to the linkstation.

Linkstation has group access and rights to folders.
FTP access to each folder is enabled and correct.
Netaccess is disabled.

Internal access via ftp is correct and logical, with any client.
External fails, with Filezilla or WinSCP

Error:

"Server sent passive reply with unroutable address. Passive mode failed."
PORT 10,100,0,81,192,180 "500 Illegal PORT command" Error:"Failed to
retrieve directory listing"

No idea why such a port should be mentioned, unless the verizon router is fixing something for me.

[davo]

If internal is working but external is failing then port 21 isn't open, simple as that. If the service is working locally then the issue is not the linkstation.

[crownfield]

But port 21 is open, and checked by http://www.canyouseeme.org/

The problem is some item that is not listed as required and therefor I do not know and check.
port 20 is not blocked, is forwarded, and shows as closed.

[joma90]

This is a suggestion as I don't have any of the new linkstations so not 100% sure if this is possible, If you can change the FTP port for Internal and External. My self, I never recommend using the common ports of FTP but that's me, I have seen people get error 500 and 453 due to some conflict with the default ports, Not sure what can cause it, most likely point to the ISP, See if that works. Its just a Suggestion. :D You can use any ports above 2000 with no issues unless your using them already, You can also try putting the Linkstation in the DMZ for a moment and test it as well. Maybe there is some FTP settings that is causing issues like SIP settings do on Voip phones.

[Eastmarch]

Port 20 would need to be forwarded as well and you must use active mode. Otherwise, it almost certainly will work in the DMZ as it is clearly a firewall issue.