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Date: Mon, 20 Nov 2023 22:35:38 -0700
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Subject: Re: Please support download setup-x86_64.exe on IPv6-only network
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From: Brian Inglis via Cygwin <cygwin@cygwin.com>
Reply-To: cygwin@cygwin.com
Cc: Brian Inglis <Brian.Inglis@Shaw.ca>
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On 2023-11-20 17:45, Lee via Cygwin wrote:
> On Mon, Nov 20, 2023 at 7:13 PM Backwoods BC via Cygwin wrote:
>>
>> On Thu, Nov 16, 2023 at 12:41 PM Brian Inglis via Cygwin wrote:
>>> The whole IP v4 internet is available as a compatibility subnet ::ffff:0:a.b.c.d
>>> on IP v6, so there is no excuse for not supporting interconnection, as it will
>>> be required until the last backbone routers drop IP v4 support.
>>
>> Just a small correction for the mail archives as this appears solved.
>> The correct IPV6 address for the IPV4 address range is
>> ::ffff:a.b.c.d  (no '0')
> 
> If you're going for correcting the record, let's make it correct.
> ::ffff:a.b.c.d is not a solution for IPv6 => IPv4 interconnection over
> the Internet.
> 
> from:  https://www.rfc-editor.org/rfc/rfc5156
> 
> 2.2.  IPv4-Mapped Addresses
> 
>     ::FFFF:0:0/96 are the IPv4-mapped addresses [RFC4291].  Addresses
>     within this block should not appear on the public Internet.

These internal addresses are used by dual stack hosts to allow clients or 
servers to handle connections to IPv4 hosts the same as IPv6 hosts.

Whereas ::ffff:0:0:0/96 == ::ffff:0:a.b.c.d allows IPv6 only hosts without 
assigned IPv4 addresses to connect to IPv4 only hosts via SIIT see:

	https://www.rfc-editor.org/rfc/rfc7915 Stateless IP/ICMP Translation.

-- 
Take care. Thanks, Brian Inglis              Calgary, Alberta, Canada

La perfection est atteinte                   Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter  not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer     but when there is no more to cut
                                 -- Antoine de Saint-Exupéry

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