Pb with nat and redirection

[zel at free.fr]

Hye !!!

Ok, yesterday, I posted a question, and someone answerd me, but, the solution 
(or what I've done to install it) failed.
Does someone could say me why ?

The situation is described below:

Ethernet
 ADSL
 modem
  o ---10.0.0.0/24--- A --- 10.1.0.0 / 24 ---
                      |
                      |
                      |
               192.168.1.0/24
                      |
                      |
                      |


A is a routing firewall computer (creating a DMZ).
(Based on a freeBsd 4.4).
Its IP addresses are
   10.0.0.1
   10.1.0.254
  192.168.1.254

Workstations are on 192.168.1.0/24 network and
servers are on 10.1.0.0/24.

ifconfig on A displays:
ep0 .......
ed1 .......
ed2 .......
tun0 ......
   .... -> ....
   .... -> ....


The FTP server is 10.1.0.1 so
natd is running on A with this parameters:
-dynamic -n tun0 -redirect_port tcp 10.1.0.1:ftp ftp

But when I try to connect to my FTP server from outside, I receive the classic 
message : "Connection closed by host", but I can access to my FTP server from 
inside.

What can I do, where is the mistake ?

Thanks.