Forward traffic from one IP address to another

The first thing to do is do enable IP forwarding. This is done either by using:

 echo "1" > /proc/sys/net/ipv4/ip_forward

or

 sysctl net.ipv4.ip_forward=1

Then, we will add a rule telling to forward the traffic on port 1111 to ip 2.2.2.2 on port 1111:

 iptables -t nat -A PREROUTING -p tcp --dport 1111 -j DNAT --to-destination 2.2.2.2:1111

and finally, we ask Iptables to masquerade:

iptables -t nat -A POSTROUTING -j MASQUERADE