IPTables
echo "net.ipv4.ip_forward = 1" >> /etc/sysctl.conf
echo "net.ipv4.conf.all.route_localnet=1" >> /etc/sysctl.conf
sysctl -p
#!/bin/sh -e
YourIP=127.0.0.1
YourExternalIP=`ifconfig | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*' | grep -v '127.0.0.1'`
YourPort=20000:30000
TargetIP=xx.xx.xx.xx
TargetPort=80
iptables -t nat -F
iptables -t nat -A PREROUTING --dst $YourIP -p tcp --dport $YourPort -j DNAT --to-destination $TargetIP:$TargetPort
iptables -t nat -A POSTROUTING -p tcp --dst $TargetIP --dport $TargetPort -j SNAT --to-source $YourExternalIP
iptables -t nat -A OUTPUT --dst $YourIP -p tcp --dport $YourPort -j DNAT --to-destination $TargetIP:$TargetPort
