sudo nano /proc/sys/net/ipv4/ip_forward set the value to "1"
sudo iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 3389 -j DNAT --to-destination 192.168.1.19
sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
sudo apt-get install iptables-persistent
Forward traffic arriving on TCP Port 3389 to the destination IP 192.168.1.19