May I enable PPPoE Pass Trought?

I'm trying to config a DSL-N14u as a bridged modem and setup a RT-N66u as the main router.

I have a lot of problems to wake up the PPPoE connection from my router and, dessesperated, I'm checking each possibility. One of hem is to enable the Passtrought for PPPoE at the DSL modem. The tip for this option say that "if a divece from the LAN want use a PPPoE connection this must be enabled" but... I'm lost.

Too many options to configure and no info at the user guide...