Port forwarding port 21 on PN Router

[#1]

Just got my service activated and running today.
I've setup my internet with the router provided by Plusnet, the Technicolor 582n.
Was just setting up port forwarding for my devices and I've noticed that I cant port forward port 21 to a local device within my network. It keeps coming up with an error saying the service is being used by another device, but when I see the active list of forwarded ports there is no such device its being forwarded to.
I found this forum topic which I believe another user is also having trouble doing it:
http://community.plus.net/forum/?topic=109688.msg938819
They came to the conclusion that port 21 is reserved for the routers usb sharing function, someone please tell me this is incorrect. How can a router in this day and age not let you forward ports as common as 21 (ftp port).

[#2]

It does appear to be the case that it's reserved for USB.Had exactly the same issue.
With that, the appalling UI, and poor WiFi performance i gave up and just bought a better router in the end.

[#3]

The router has an built-in ftp server - Make sure it's disabled in Home > Toolbox > Content Sharing

[#4]

Quote from: DaveyH

It does appear to be the case that it's reserved for USB.Had exactly the same issue. With that, the appalling UI, and poor WiFi performance i gave up and just bought a better router in the end.

I had hoped this was not correct, the wifi isnt much of an issue as I have an access point upstairs.. I guess I'm gonna have to fork out some more money now to get a decent router.

Quote from: pwatson

The router has an built-in ftp server - Make sure it's disabled in Home > Toolbox > Content Sharing

Yep I did that too, I think even if its disabled the port is reserved for this function.

[#5]

Once you've turned it off
Go to Game and Application sharing and you'll see FTP there -  unassign it and then you can re-assign it.

[#6]

Your right, SSH being one of them.
The main reason I want FTP access is for my NAS (Synology) which only really supports FTP for multiple users.
SSH can be added but it means I will have to hack it, and jail every user.
dick:quote