PPPoE and Nat w/masquerade

Hello,

I have 750g that acts as pppoe server and assigns public IP’s when a user authenticates. Now I want dhcp users to obtain private IP on of Lan side from dhcp server and masquerade and nat to the ether1-gateway interface IP which is the “public” IP for pppoe server. Can this be done?

As soon as I enable Nat then pppoe server stops allowing users to authenticate. I believe it is Firewall rule but not sure how to apply.

TIA for your help.