iptables | badllama.com

Port-based Redirect

assuming 10.2.3.4 is the ip of the box we are redirecting to and 10.2.3.5 is the ip of the box handling the redirect. Forwarding port 3306

echo "1" > /proc/sys/net/ipv4/ip_forward
iptables -P FORWARD ACCEPT
iptables -A FORWARD -i eth0 -p tcp --dport 3306 -j ACCEPT
iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 3306 -j DNAT --to-destination 10.2.3.4:3306
iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source 10.2.3.5

To undo this

iptables -D FORWARD -i eth0 -p tcp --dport 3306 -j ACCEPT
iptables -t nat -D PREROUTING -p tcp -i eth0 --dport 3306 -j DNAT --to-destination 10.2.3.4:3306
iptables -t nat -D POSTROUTING -o eth0 -j SNAT --to-source 10.2.3.5