Hello,
Jon Wilson a écrit :
Kristofer wrote:
I've googled and done some searches, and the only information I can
find is for port forwarding with NAT. Perhaps that's what I need to
accomplish what I am trying to do.
I currently have an SMTP server listening on port 25, and the machine
has its own static IP address, no NAT is being used.
I want to use iptables to forward inbound traffic on port 587 to port
25 of that same machine, so basically making SMTP listen on both
ports. I do not wish to configure the SMTP software to listen on
multiple ports, since I may want to open up several more ports in the
future and that would be a lot of idle daemons listening on ports they
may or may not use.
Huh ? What is that SMTP software which requires tu run one separate
daemon for each listening port ? If it can use inetd, you can have it
listening on multiple ports even without a single idle daemon running
(except inetd itself of course).
So, my questions is: how can I have incoming traffic on port 587 go to
port 25 of the localhost?
Port forwarding is a form of destination NAT. It can also be done with a
TCP relay such as 6tunnel, but the final destination sees only the relay
address, not the original source address. Not very convenient for
logging or access control.
if iptables on the same computer as the smtp server:
iptables -t nat -A PREROUTING -p tcp --dport 587 -m state --state NEW -d
$IP_OF_MAIL_SERVER -j REDIRECT --to-ports 25
else:
iptables -t nat -A PREROUTING -p tcp --dport 587 -m state --state NEW -d
$IP_OF_MAIL_SERVER -j DNAT --to $IP_OF_MAIL_SERVER:25
Note that the second rule also works on the server itself.
-
To unsubscribe from this list: send the line "unsubscribe netfilter" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
