I am using an Ubuntu Computer as a Router.
It has a network connected locally on
eth0 and is also connected to the internet with another interface and inside of an OpenVPN.
I set up NAT port forwarding, so I can reach a few of the devices in the attached subnet.
sudo iptables -A FORWARD -o eth0 -i tun0 -j ACCEPT sudo iptables -A FORWARD -o eth0 -i tun0 -j ACCEPT sudo iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE sudo iptables -t nat -A PREROUTING -p udp -i tun0 --dport 14550 -j DNAT --to-destination 192.168.1.50:60000 sudo iptables -t nat -A PREROUTING -p tcp -i tun0 --dport 5000 -j DNAT --to-destination 192.168.1.2:5000
From the subnet I can reach the internet fine and from any other computer I can reach the TCP server that is being forwarded to port 5000.
The Ubuntu routers eth0 interface has the IP 192.168.1.1 and the UDP server the IP 192.168.1.50.
I can't figure out how to get UDP forwarding to work.
tcpdump shows me that the UDP server inside the subnet is active and it can and does communicate to the ubuntu computer that acts as the router.
Just when I try to reach it from the outside, I get nothing.