Ubuntu networking: can't connect to LAN

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http://unix.stackexchange.com – I have a server with Zentyal 3.03 (Ubuntu 12.04) LTS. It has 3 network devices: eth0 - dhcp fast internet (I pay for it) eth1 - static slow internet (it's free for the school) eth2 - LAN I can reach the server with SSH, but I can't reach a LAN server from outside. I have set up portforwarding for port 80, it made no sense. I used: sudo iptables -A FORWARD -p tcp -i eth1 --sport 8888 -o eth2 -d -dport 8888 -j ALLOW I don't know what can help, please ask what to show you. Please help me and do not send me to an another stackexchange website. (this wolud be the 4th time) (HowTos)