> I have workt with a lot of ruters, gateways and firewalls
> but this m0n0wall is strange.
> I have tryed now for some time to NAT any port from my external / public IP
> to a server on my intra network.
In my experience, m0n0wall is broken in a way that causes the firewall
filter engine to see both translated and non-translated addresses.
To make NAT work on m0n0wall, I created twice all rules that pertain
to networks and devices with NATed addresses - one rule using the
translated address and one rule using the untranslated.