On Mon, 22 Jul 2019, Owen DeLong wrote:
2. It was decided that the effort to modify each and every IP stack in order to facilitate use of this relatively small block (16 /8s being evaluated against a global run rate at the time of roughly 2.5 /8s per month, mostly to RIPE and APNIC) vs. putting that same effort into modifying each and every IP stack to support IPv6 was an equation of very small benefit for slightly smaller cost. (Less than 8 additional months of IPv4 free pool vs. hopefully making IPv6 deployable before IPv4 ran out).
Well, people are working on making 240/4 usable in IP stacks: https://raw.githubusercontent.com/dtaht/unicast-extensions/master/rfcs/draft... There have been patches accepted into some BSDs and into Linux tools/kernel and other operating systems to make 240/4 configurable and working as unicast space. I don't expect it to show up in DFZ anytime soon, but some people have dilligently been working on removing any obstacles to using 240/4 in most common operating systems. For controlled environments, it's probably deployable today with some caveats. I think it'd be fine as a compliment to RFC1918 space for some internal networks. -- Mikael Abrahamsson email: swmike@swm.pp.se