Problem of newbee !!!

[zel at free.fr]

Here is my problem:

My config is described below:
P100 + FreeBSD 4.4
for DMZ job

ep0 (10.0.0.1) to Internet
ed1 (10.1.0.254) gateway for 10.1.0.0/24 network (servers...)
ed2 (192.168.1.254) gateway for 192.168.1.0/24 network (workstations...)

So currently, connected with an ethernet ADSL modem to the Internet, I 'natd'
all packets out and incoming...

But now, I would like transfer all ftp request to one server behind DMZ...
ftpd is running (on 10.1.0.1)

I read man and some informations on forums about natd and so, I tried:
natd -redirect_port tcp 10.1.0.1:20-21 20-21

I tried few other commands but I always have the same answer:
natd: aliasing address not given ...

What can I do ? Is the soft I currently try to use, the good one to do what I
want to do ???

Please, help...

Thanks..

Sylvain