Port forward to Flashforge Finder via OctoPrint (RPI) (remote printing)

#enable IP forwarding:
sudo sed -i 's/#net.ipv4.ip_forward=1/net.ipv4.ip_forward=1/g' /etc/sysctl.conf

#then activate the changes
sudo sysctl -p

#Start iptables
sudo systemctl start iptables

#Check iptables rules
(check that you don't have a deny policy )

#You can flush all rule to start in a clean env:
sudo iptables -F
#+For the nat sudo iptables -t nat -F

#Add rules
sudo iptables -t nat -A POSTROUTING --out-interface w**** -j MASQUERADE
sudo iptables -A FORWARD --in-interface eth0 -j ACCEPT
sudo iptables -t nat -A PREROUTING -p tcp -i eth0 -m tcp --dport 9000 -j DNAT --to-destination 10.10.100.254:8899
sudo iptables -t nat -A PREROUTING -p tcp -i eth0 -m tcp --dport 8080 -j DNAT --to-destination 10.10.100.254:80

#To check :
sudo iptables -t nat -L -n

#Save the iptables rule :
sudo iptables-save | sudo tee /etc/iptables.up.rules

You will reach the printer via ip number of Raspberry Pi and the port that is 9000
You will reach the webserver of the printer via Raspberry Pi ip and the port 8080
Enjoy!

source: https://serverfault.com/questions/93...-two-interface