Comcast will happily hand out a prefix delegation larger than a /64 if you ask for it, and set the prefix delegation request to 1 instead of 0. This is done be

Comcast will happily hand out a prefix delegation larger than a /64 if you ask for it, and set the prefix delegation request to 1 instead of 0. This is done because many routers were built with bad IPv6 support that requested a /48 even though they only needed a single /64 for a LAN and Comcast was handing out /60's (their largest size) like candy with almost no use. So my config was to request two prefix delegation, one tagged 0, which would always get a /64, and then one tagged 1 which would get a /60. Not sure if you still can do it or not, but at one point you could continue to ask for prefix delegations (/60's) and get even more address space. Here's the dhcp6c.conf: interface em0 { send ia-pd 0; send ia-pd 1; send ia-na 1; }; id-assoc pd 0 { prefix ::/64 infinity; prefix-interface lagg0 { sla-id 0; sla-len 0; }; }; id-assoc pd 1 { prefix ::/60 infinity; prefix-interface vlan10 { sla-id 1; sla-len 4; }; prefix-interface vlan11 { sla-id 2; sla-len 4; }; prefix-interface vlan20 { sla-id 3; sla-len 4; }; prefix-interface vlan21 { sla-id 4; sla-len 4; }; prefix-interface vlan22 { sla-id 5; sla-len 4; }; }; id-assoc na 1 { }; Note: ia-pd 0 will only ever pull a /64, even if you ask for a /60 all you'll ever get back is a /64. ia-pd 1 on the other hand will allow you to pull anywhere from a /64 to a /60. Yes, this means you get 16 + 1 /64's to use. On top of that I pull a single /128 for the external interface of my router.