Forward (redirect/nat) traffic with iptables

If you want to redirect all traffic to IP 1.1.1.1 to IP 2.2.2.2, it simply can be done with iptables.
You can also redirect traffic to specific port by specifying a port instead of range.
First of all enable IP forwarding in /etc/sysctl.conf on 1.1.1.1 host:

net.ipv4.ip_forward=1

Execute following for the changes to take effect:

sysctl -p

add iptables rules

iptables -A FORWARD -d 2.2.2.2 -i eth0 -p tcp -m tcp --dport 7789 -j ACCEPT
iptables -A FORWARD -d 2.2.2.2 -i eth0 -p udp -m udp --dport 7789 -j ACCEPT
iptables -t nat -A PREROUTING -d 1.1.1.1 -p tcp -m tcp --dport 7789 -j DNAT --to-destination 2.2.2.2
iptables -t nat -A PREROUTING -d 1.1.1.1 -p udp -m udp --dport 7789 -j DNAT --to-destination 2.2.2.2
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

NOTE: FOPRWARD in section ":FORWARD ACCEPT", PREROUTING and POSTROUTING in ":OUTPUT ACCEPT" Restart iptables

service iptables restart

Here is an example of working iptables:

# Generated by iptables-save v1.4.7 on Tue Apr  9 14:27:04 2013
*filter
:FORWARD ACCEPT [0:0]
-A FORWARD -d 2.2.2.2 -i eth0 -p tcp -m tcp --dport 23:65500 -j ACCEPT
-A FORWARD -d 2.2.2.2 -i eth0 -p udp -m udp --dport 23:65500 -j ACCEPT
COMMIT
# Completed on Tue Apr  9 14:27:04 2013
# Generated by iptables-save v1.4.7 on Tue Apr  9 14:27:04 2013
*nat
:PREROUTING ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A PREROUTING -d 1.1.1.1 -p tcp -m tcp --dport 23:65500 -j DNAT --to-destination 2.2.2.2
-A PREROUTING -d 1.1.1.1 -p udp -m udp --dport 23:65500 -j DNAT --to-destination 2.2.2.2
-A POSTROUTING -o eth0 -j MASQUERADE
COMMIT
# Completed on Tue Apr  9 14:27:04 2013

Warning: Make sure your ssh port is out of range 23:65500, otherwise you will lose ssh access to 1.1.1.1. ""