Firewallrules for a gentoo box with 4 nics

[homer_2008@gmx.net]

Hi list,

I am playing with a little gentoo box installed on a pcengine alix board with four nics. I need to secure it with the iptables firewall. Here is the configuration of the nics:
------------------------------------------------------------
1. eth0 (internal trusted network)
2. eth1,ppp0 (internet DSL (ppp0) with DHCP IP address changing every 24 hours)
3. eth2 (a DMZ Zone with a single Webserver)
4. wlan0 (miniPCI atheros card)(Wireless LAN interface only webtraffic should be enabled)

------------------------------------------------------------
InternetDSL --> eth1(carrier)ppp0 
Internal network --> eth0
DMZ --> eth2
------------------------------------------------------------
From the internet all ports should be closed accept all related,established connections. One port should be open for openvpn 1194/udp.

The internal network should have open the DHCP,DNS,HTTP ports.

The wireless wlan0 nic should only have open the port 80 for webtraffic.

The DMZ should only have the ports open for the webserver.

NAT should be from the internet (ppp0,eth1) to the internal network (eth0) and eth2(DMZ)
------------------------------------------------------------
the ips for the nics should be the following:

eth0 - internal - 192.168.0.0/24
eth1(ppp0) - DHCP because DSL IP is changing every 24 hours.
eth2 - 172-16.0.0/24

------------------------------------------------------------

My question to the list is, how can I realize this idea with iptables?

I hope you help me on this task.

Homer

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