http://www.dslreports.com/forum/r20048672 en Thu, 10 Dec 2009 12:39:57 EDT Thu, 10 Dec 2009 12:39:57 EDT http://www.dslreports.com/forum/remark,20058530 upb : I've encountered this problem in the DSL-2540B router, and there is no workaround for it. Only a firmware upgrade has a chance of success.

The problem lies in the Netfilter modules used by the Linux kernel (the router uses Linux as its O/S). There is a particular module (ip_conntrack_ftp) which is supposed to be notified if a non-standard ftp port is to be put in use so that it can properly rewrite the ftp packets. Unfortunately, the module has been compiled in such a way that it will not accept an alternative ftp port, and you're stuck with port 21 even if you attempt to use passive mode. I discovered the problem while telneted to the router and using command line "insmod" and "iptables ..." commands.

I happen to use a non-standard ftp port for security reasons from time to time (I don't like every Tom, Dick, and Harry beating on my ftp server), and I use a different router when that's necessary. Otherwise, I use secure FTP (a part of Secure Shell, or ssh), and it doesn't require any special packet rewriting to work. I'd recommend running an ssh server in sftp mode if you can manage it.

Good luck.]]> http://www.dslreports.com/forum/remark,20058530 Mon, 25 Feb 2008 12:34:46 EDT http://www.dslreports.com/forum/remark,20055503 anon : Yes. I have assigned another port to the FTP Server in the Router Configuration. However, It did not work properly.]]> http://www.dslreports.com/forum/remark,20055503 Sun, 24 Feb 2008 20:38:33 EDT http://www.dslreports.com/forum/remark,20053325 pleekmo : Port 21 is the standard port for FTP. For FTP to work using some other port you must assign it so in both the router and FTP client and/or server.
--
HCN: Because you deserve a rest!

Proud member of the Free Omelas Liberation Front.]]> http://www.dslreports.com/forum/remark,20053325 Sun, 24 Feb 2008 12:29:29 EDT http://www.dslreports.com/forum/remark,20048672 anon : Hello all,
I found that the ftp server cannot work under the ports except 21. I just wanna know is it any solutions for this? Thanks.

Thomas LEe]]> http://www.dslreports.com/forum/remark,20048672 Sat, 23 Feb 2008 13:15:44 EDT