Re: Generic anycast addresses...

[Ted Lemon <[e-mail]>]

On Jul 12, 2019, at 9:57 AM, Ted Lemon <[e-mail]> wrote:
> Apparently I just can’t type IPv6 addresses.   Let’s try this one more time: 2001:1::/64.   But actually it looks like it’s 2001:1::/32.   This isn’t specifically stated anywhere, so we don’t really know, but the next non-/128 allocation is the next /32.

There’s no way to answer definitively.   Certainly the remainder of the /32 is unallocated.   However, the next thing that’s allocated is explicitly a /48, and the thing that follows that is a /32.   So 2001:2::/48 is allocated, but the rest of 2001:2::/32 is not.   If a /64 were needed, the IANA could decide to allocate 2001:1:0:1::/64 and this would not create a conflict.   But since this isn’t stated explicitly, we don’t know, and it’s entirely possible that IANA would not allocate that /64, since they probably don’t know either.

For reference, here’s the part of the table I’m talking about:

2001::/23	IETF Protocol Assignments	[RFC2928 <http://www.iana.org/go/rfc2928>]	2000-09	N/A	False [1 <https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml#note1>]	False [1 <https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml#note1>]	False [1 <https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml#note1>]	False [1 <https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml#note1>]	False
2001::/32	TEREDO	[RFC4380 <http://www.iana.org/go/rfc4380>] [RFC8190 <http://www.iana.org/go/rfc8190>]	2006-01	N/A	True	True	True	N/A [2 <https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml#note2>]	False
2001:1::1/128	Port Control Protocol Anycast	[RFC7723 <http://www.iana.org/go/rfc7723>]	2015-10	N/A	True	True	True	True	False
2001:1::2/128	Traversal Using Relays around NAT Anycast	[RFC8155 <http://www.iana.org/go/rfc8155>]	2017-02	N/A	True	True	True	True	False
2001:2::/48	Benchmarking	[RFC5180 <http://www.iana.org/go/rfc5180>][RFC Errata 1752 <http://www.rfc-editor.org/errata_search.php?eid=1752>]	2008-04	N/A	True	True	True	False	False
2001:3::/32	AMT	[RFC7450 <http://www.iana.org/go/rfc7450>]	2014-12	N/A	True	True	True	True	False
If your MUA rendered this incomprehensibly, here’s the actual URL for convenience: https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml <https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml>