CC: s to Non List Members (was Re: 202203080924.AYC Re: 202203071610.AYC Re: Making Use of 240/4 NetBlock)

John Gilmore gnu at
Wed Mar 9 09:16:22 UTC 2022

John Levine <johnl at> wrote:
> FWIW, I also don't think that repurposing 240/4 is a good idea.  To be
> useful it would require that every host on the Internet update its
> network stack, which would take on the order of a decade...

Those network stacks were updated for 240/4 in 2008-2009 -- a decade
ago.  See the Implementation Status section of our draft:

Major networks are already squatting on the space internally, because
they tried it and it works.  We have running code.  The future is now.
We are ready to update the standards.

The only major OS that doesn't support 240/4 is Microsoft Windows -- and
it comes with regular online updates.  So if IETF made the decision to
make it unicast space, most MS OS users could be updated within less
than a year.

> It's basically
> the same amount of work as getting everything to work on IPv6.

If that was true, we'd be living in the IPv6 heaven now.

It doesn't take any OS upgrades for "getting everything to work on
IPv6".  All the OS's and routers have supported IPv6 for more than a

Whatever the IPv6 transition might require, it isn't comparable to the
small effort needed to upgrade a few laggard OS's to support 240/4 and
to do some de-bogonization in the global Internet, akin to what CloudFlare
did for


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