I would like to forward port 81 from 192.168.0.1 which is connected to the net to 192.168.0.4 using iptables.

I've looked aroud, found a few command lines but they don't work :\

can anyone give me THE command line that will work for sure
or recommand me a good iptables guide?


thanx

Port forwarding would look something like this...
iptables -t nat -A PREROUTING -i $EXT -p tcp --dport 80 -j DNAT --to 192.168.0.4

But I'm kind of wondering in if you just want to share the internet connection. If so, you don't use port forwarding, but this instead....

# Use this for NAT or IP Masquerading.
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o $EXT -j MASQUERADE

# This rule will accept connections from local machines.
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -s 192.168.0.0/24 -d 0/0 -p all -j ACCEPT

the connection is already shared and now I just want to forward port 81 to 192.168.0.4

I'm gonna try your command thx =)

Just keep in mind that $EXT is for my setup and you might use just the external interface ( eth0 ) or ( eth1 ).

it doesn't work :\

do I need to restart iptables? to reboot?

Reboot is a windows thing.
Just curious, what port is 81 for? my ISP blocks all of the well know ports so I would have to use a high number.

This site has a lot of tables information.....

http://www.linuxguruz.com/iptables/

81 is the port of my alternativ webserver (the main one is on 80) I tried with port number 8192 and I still have the problem