IP Port Forwarding

check:
cat /proc/sys/net/ipv4/ip_forward

enable:

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

Example iptables rules: (forward port 81 to 192.168.60.10:80)

/usr/sbin/iptables -A FORWARD -p tcp --dport 80:80 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
/usr/sbin/iptables -t nat -A PREROUTING -p tcp --dport 81:81 -j DNAT --to 192.168.60.10:80