[talk] Whaaaaa? Unicast Use of the Formerly Reserved 127/8

Isaac (.ike) Levy ike at blackskyresearch.net
Fri Nov 19 14:51:03 EST 2021

On Fri, Nov 19, 2021, at 2:33 PM, N.J. Thomas wrote:
> * Isaac (.ike) Levy <ike at blackskyresearch.net> [2021-11-19 14:13:25-0500]:
>> "This document provides history and rationale to reduce the size of
>> the IPv4 local loopback network ("localnet") from /8 to /16, freeing
>> up over 16 million IPv4 addresses for other possible uses."
> Years ago, before v4 exhaustion, similar calls were made made to request
> organizations like MIT to give up their /8 IP allocations and the
> standard response from all the network engineers was that it would only
> delay the inevitable for a few months at most.
> The IPv4 pool was completely exhausted a few years ago, so even if this
> proposal would be accepted (I strongly doubt it would be), it would be a
> small band-aid applied to a gushing wound.
> (MIT did eventually sell off a large chunk of their /8 a few years ago
> for lots of $$$. They probably should have waited, it's worth a lot more
> now.)
> As much as I am annoyed with IPv6 (lack of backwards compatibility being
> its biggest wart), it is the way to go; any other attempts such as this
> draft, and you're only complicating matters. We now have NAT, CGNAT
> (https://en.wikipedia.org/wiki/Carrier-grade_NAT) and the amazing STUN:
>     https://en.wikipedia.org/wiki/STUN
> to fix the problems we created trying to fix the problem. =-)
> As expected, this proposal is being excoriated on NANOG, so I'll leave
> it to you fine folks to look up that discussion. I'll just quote the
> inimitable John Levine on the subject:
>     The amount of work to change every computer in the world running
>     TCP/IP and every IP application to treat 240/4 as unicast (or to
>     treat some of 127/8) is not significantly less than the work to get
>     them to support IPv6. So it would roughly double the work, for a 2%
>     increase in the address space, or for 127/8 less than 1%.  The code
>     for IPv6 is already written, after all.
>     Also, while the world has run out of free IPv4 address space, there
>     is plenty of IPv4 if you are willing to pay for it. A 2% increase in
>     v4 addresses would not change that.
> Thomas
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I'm delighted that your stats reinforce my knee-jerk reaction to this draft.


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