How to DMZ with PPPoE?

Hi,

I’ve been searching for this without any success. This is my scenario:

I have a Local interface (192.168.2.1/24) with several computers and one multimedia server (192.168.2.2). On the other side I have a PPPoE connection that gets a DHCP IP address (from ADSL modem).

And my problem: How can I redirect all incoming port connections to the multimedia server 192.168.2.2 if I don’t know the PPPoE connection IP? In other words, how to create a DMZ for 192.168.2.2 if I have dhcp on wan interface?

I know how to do it if WAN ip is static, but I can’t handle it when I only know the interface.

Thanks.

in-interface=PPPoE dst-address-type=local