Native IPv6 with dynamic /56 range

[tenortim]

For those still encountering issues with Comcast's odd DHCPv6 setup
FYI, another trick to doing this if you don't want to have to change the MAC address and aren't willing to wait a week:

Modify the WAN dhcp settings to request a /60 as previously detailed
Download http://www.ipv6.mtu.edu/wide_mkduid.pl which is a simple perl script to create a dhcp6c_duid file.
Run it on a Linux box (or something with Perl installed) like so
$ ./wide_mkduid.pl -t now -m <pfsense wan="" mac="" address="">successfully created /home/timw/dhcp6c_duid
DUID is 00:01:00:06:55:77:0a:34:XX:XX:XX:XX:XX:XX (MAC redacted)

copy over the generated dhcp6c_duid to the pfsense box (I scp'd it into /tmp)
Save a copy of /var/db/dhcp6c_duid (just in case anything goes wrong)
cp /tmp/dhcp6c_duid /var/db/dhcp6c_duid
Go into the WAN settings in the Web UI and just resave them.

Immediately after doing this I was received my shiny new /60 prefix delegation.</pfsense>