for setup see This PDF, slide 4. (Interface addresses vary, as this slide was made to describe the problem, and DHCP spoofing turned out to be the solution – almost)
The wireless AP is also DHCP server for the LAN domain.
I managed to get DHCP spoofing working as per the instructions on this site. All internet trafic is forwarded from the SpeedTouch to the WAN port of the AP, and arrives at my PC (shown by my personal firewall).
Outgoing PING works also, if I specify an IP address, but not when I specify a name. Somehow, my DHCP clients (XP Home) have no access to the DNS servers of my provider. Which way does a DNS request travel through this setup.
PS I am lucky to have a spare Alcatel PRO, so switching setups is fairly easy. I am now using the setup in slide 1 again…