240/4 (Re: 44/8)

[Mikael Abrahamsson <swmike () swm pp se>]

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-gilmore-taht-v4uniext.txt

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