Can't get port forwarding to work on Ubuntu

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http://serverfault.com – I'm using my home server as NAT/router, which works well. But now I'm trying to forward port 3478, which I can't get to work. eth0 = public interface eth1 = private network $ cat /proc/sys/net/ipv4/conf/eth0/forwarding 1 $ cat /proc/sys/net/ipv4/conf/eth1/forwarding 1 Then to forward port 3478 to, I read somewhere that I should run iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 3478 -j DNAT --to-destination iptables -A FORWARD -p tcp -d --dport 3478 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT I also ran ufw allow 3478 But testing port 3478 (HowTos)