Original bug filed by compaq963 on 2013-12-31 in Bugzilla, copied here so that it doesn't get lost/forgotten (will also copy in comments):
It would be great to see Prefix delegation support in VyOS. Prefix delegation is needed for IPv6 with many ISPs because this is how they hand out prefixes.
Also, It would be great to allow you set a custom IA_PD prefix. An example is my ISP will hand out a /60 to you with a custom IA_PD prefix. If you just accpet the default you get a /64.
One solution is using WIDE-DHCPv6. The project page is at http://wide-dhcpv6.sourceforge.net/