Using ZyXEL ADSL modem and DD-WRT router

[jrhnewark]

I'm trying to use a ZyXEL P-660R-D1 modem as an ADSL gateway an a Buffalo router running DD-WRT as the LAN router (I want to use DD-WRT for the QoS features that the basic O2 router provided with my connection doesn't provide).

I can't work out how to make port forwarding/NAT work. I've put the router as the 'default server IP' address within the ZyXEL GUI which apparently puts it into the DMZ and I assume should make all traffic go to the router but it doesn't seem to work.

I've made the ZyXEL modem 10.1.1.1/255.255.255.0 and the Buffalo router 10.0.0.1/255.255.255.0.

Basically, all I want is the ZyXEL modem to be pass-through to the Buffalo router, to just be the ADSL gateway in the same way my cable modem was!!

I've tried putting it into bridge mode but this doesn't seem to give me the options to let me configure the ADSL connection.

Any ideas would be great.