The FreeBSD kernel does not support PPPoA authentication over an
ethernet link. This is required for Ethernet ADSL modems operating in
'Bridge' mode together with BSD Firewalls. (USB modems are not desirable
as they are unreliable and their drivers are often released under
restrictive licences)

This is a growing issue in the UK and in other countries, where PPPoA
is the standard used for ADSL authentication. FreeBSD firewalls are
increasingly common and available to home users through the m0n0wall
and pfSense projects.

For reference, m0n0wall is based on FreeBSD 4.11 and pfSense on FreeBSD
6.0 HEAD. PPPoA authentication support is not present in the kernel of
any FreeBSD release. In addition, almost all ADSL modems available in
the UK support bridge mode, and so could be used with a FreeBSD firewall.

Finally, Linux does have support for PPPoA authentication, but as usual
it is in the form of an ugly and complex 'extension' to the current PPP
software which is difficult to use. FreeBSD could again put itself ahead
of the game by having a full BSD-licensed kernel-level implementation
of RFC2364.

A few References (people with this problem):

http://lists.freebsd.org/pipermail/freebsd-atm/2005-June/000108.html
Trying (and failing) to use a Ethernet ADSL modem with PPPoA and FreeBSD.

http://m0n0.ch/wall/list/?action=show_msg&actionargs[]=53&actionargs[]=37
http://m0n0.ch/wall/list/?action=show_msg&actionargs[]=47&actionargs[]=42\
Asking if PPPoA authentication support exists in m0n0wall/FreeBSD.

http://www.m0n0.ch/wall/list/?action=show_msg&actionargs%5B%5D=67&actionargs%5B%5D=41
http://m0n0.ch/wall/list/?action=show_msg&actionargs[]=178&actionargs[]=06
http://m0n0.ch/wall/list/?action=show_msg&actionargs[]=57&actionargs[]=17
Having issues with buggy DHCP Spoofing method as PPPoA authentication is not supported under m0n0wall/FreeBSD.

Fix: 

Implement PPPoA authentication within the FreeBSD kernel.
How-To-Repeat: N/A (Feature request)