Re: Mapping plan
Why should a DHCPv4 server carry IPv6 information?
Adam. Eve. Snake. Dinosaurs next to them. v6 Autoconfig. Goodness. Half of the parameters missing. Still goodness because scriptures say so. Asking DHCPv6. Half of the parameters conflict. Still goodness because the holy scriptures say so in RFC6214.
The core issue here is that autoconfig has the implicit assumption that routers should supply configuration information and vice versa. That assumption is "your ship of fail has arrived" for proper network management. Big time. This was something which became absolutely clear when DHCP become the de-facto standard for v4 management combined with things like DHCP to DNS integration, option 82, etc. 15 years ago to be more exact. That was the point when autoconfig should have been buried 6 feet under with a stake through it so it does not get up.
Autoconfig is a big fail in a modern campus architecture today where you may deploy vlan choice, broadcast isolation and/or multicast limitations based on the actual DHCP events and specifically option 82 in its "authenticated client ID" incarnation.
Shipping full v6 info in DHCPv4 allows you to reuse existing layer 2 legacy infrastructure including things like option 82 without replacing all of it because the holy prophet* of v6 said so. It just works and if it was done, we would have had 40%+ of hosts on v6 by now instead of having technoreligious arguments with evangelicals which continue to explain that the holy sepulture, err simultaneous coexistence of autoconfig, DHCPv4 and DHCPv6 is somehow a good idea.
The holy prophet is usually depicted as a Fred Bake-like charging rhinoceros accompanied by a large number of Homenet attendees in acolytes garb.