problems with iptables redirect of ssh

[Luca Ferrari]

Hi all,
after a while I ended up with a following iptables configuration, that is the 
following:

luca at backup$ iptables-save

:PREROUTING ACCEPT [33878969:5627323255]
:POSTROUTING ACCEPT [689881:100132957]
:OUTPUT ACCEPT [8099059:546320333]
-A PREROUTING -p tcp -m tcp --dport 2222 -j REDIRECT --to-ports 22
COMMIT

that is obtained from the following:

$IPTABLES -F OUTPUT
$IPTABLES -F INPUT
$IPTABLES -F FORWARD
$IPTABLES -t nat -F PREROUTING
$IPTABLES -t nat -F POSTROUTING
$IPTABLES -P INPUT ACCEPT
$IPTABLES -P OUTPUT ACCEPT
$IPTABLES -P FORWARD ACCEPT
$IPTABLES -t nat -I PREROUTING -p tcp --dport 2222  -j REDIRECT --to-ports 22

Now, what I'd like to obtain is to forward the connection to the 2222 port to 
the 22, but when I try to connect I get:

telnet localhost 2222
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection refused

It seems to me strange, since the default policy should be accept, and the 
connection should be redirected to the ssh port (that is working, I can 
connect to it). Any idea on that? I'm using ubuntu 7.1.

Thanks,
Luca