[188056] in North American Network Operators' Group
Re: IPV6 planning
daemon@ATHENA.MIT.EDU (Owen DeLong)
Mon Mar 7 18:52:14 2016
X-Original-To: nanog@nanog.org
From: Owen DeLong <owen@delong.com>
In-Reply-To: <CAPkb-7AnQ1N-hDAc9zgtj-wJuAjo_JuOY2b31Z0xPC=RrYUWGA@mail.gmail.com>
Date: Mon, 7 Mar 2016 15:51:06 -0800
To: Baldur Norddahl <baldur.norddahl@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces@nanog.org
> On Mar 6, 2016, at 17:57 , Baldur Norddahl <baldur.norddahl@gmail.com> =
wrote:
>=20
> Den 6. mar. 2016 13.41 skrev "Karl Auer" <kauer@biplane.com.au>:
>=20
>> Dunno about "harsh", but RFC 2464, section 4 says that the prefix =
must
>> be 64 bits. By (extremely strong) implication, a host must not use a
>> prefix of any other length to perform SLAAC. I say "extremely strong"
>> because the entire description of how an IPv6 Ethernet interface
>> identifier is formed depends on it being composed of the prefix plus =
an
>> EUI-64 identifier. Later RFCs firm up the requirement and apply it in
>> other contexts.
>=20
> But the most popular OS (Windows) completely ignores all of that and =
makes
> up an identifier not based on EUI-64. Everyone are happy anyway. The =
RFC
> should have let identifier selection as an implementation detail as =
the
> risk of collision is almost non existent given a sufficient random
> selection and we have duplicate address detection as a safeguard.
To the best of my knowledge, Windows actually generates three =
addresses=E2=80=A6
1. Subnet Stable quasi-randomized address unrelated (or at least not =
reversable to) MAC address.
2. Privacy address which rotates frequently (for some definition of =
frequently).
3. Stable address related to MAC address.
The 3rd one is standard SLAAC.
The second one is standard privacy extensions.
THe first one is unique to Windows. You=E2=80=99ll get the same address =
every time you connect to the same subnet, but you won=E2=80=99t see =
that suffix for that host on any other subnet.
Owen
