With firmware version 6.83 or above the FRITZ!Box 7430 and other VDSL models have the option to allow for PPPoE passthrough.
This configuration allows the FRITZ!Box to sit in front of another firewall or router to create a layer 2 bridge that inserts a VLAN ID of 10, then strips the VLAN tag when handing traffic back to the router. This means that the router or firewall behind the FRITZ!Box can simply operate as a PPPoE initiator, DHCP or fixed IP address (service provider dependent) without the added hassle of configuring virtual sub interfaces.
How to do it.
- After applying the latest firmware available to the FRITZ!Box follow the initial setup wizard to select language and country then allow it to restart.
- Once rebooted log back into the WebUI, cancel and exit the setup wizard then go to Internet > Account information.
- Set Internet service provider as Other Internet service provider and set the Connect via option to Connection to a DSL line
- Ensure that the page is in Advanced View mode by checking at the bottom left of the page. If this says View: Standard then click on those words to toggle to View: Advanced.
- Change the Account Information > Is account information required? option to No.
- Expand Change connection settings and set Connection Settings with VLAN 10, VPI 0, VCI 100 and encapsulation type as Bridged.
- Ensure that the Connected network devices are also allowed to establish their own Internet connections box is checked under PPPoE Passthrough.
- Remove the tick from Check the Internet connection after "Apply" has been clicked box and click Apply.
The FRITZ!Box is now in bridged PPPoE passthrough mode and is ready for the WAN port of another router to be attached to the FRITZ!Box LAN port. That other router can now initiate a PPPoE connection without need to insert VLAN tag and have the site's public IP address appear directly on its WAN interface.