Endian-FireWall as VM on VMWare-Server2 (pppoe)

Hallo

I have to install my FireWall (www.endian.it) on a VM. The Host-OS is Ubuntu-Server 8.04 LTS 

For the DMZ and the LAN the Network ist bridged and it works. But the WAN-Interface comunikates with the ADSL-Modem with the PPPOE-Protocol. How can I Configure this Network-Interface, that it works and comunicate only with the FireWall-VM (PPPOE) and not with the Host?

When I configure it as Bridge, it does not work.

I will that the Host (Ubuntu-Linux) can not see the WAN- and DMZ-Interface directly.

Can anyone help me for this Problem?

Thanks

rost21A