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Re: 64bit MAC addresses and SLAAC

Alexandre Petrescu <alexandre.petrescu@gmail.com> Wed, 17 June 2020 11:39 UTC

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Subject: Re: 64bit MAC addresses and SLAAC
To: Bob Hinden <bob.hinden@gmail.com>
Cc: IPv6 List <ipv6@ietf.org>
References: <e8a25961-5ac9-d35e-77dd-bf86f45cd077@gmail.com> <a17ae9f3-001c-07f6-84f9-a0ca583e6a00@gmail.com> <7AE5B6D0-AB01-4077-A9EF-5BD86F428681@gmail.com>
From: Alexandre Petrescu <alexandre.petrescu@gmail.com>
Message-ID: <7a3b839f-099e-8fd3-35a2-4625df3c369e@gmail.com>
Date: Wed, 17 Jun 2020 13:39:09 +0200
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Le 15/06/2020 à 23:01, Bob Hinden a écrit :
> Alexandre,
> 
>> On Jun 15, 2020, at 1:23 PM, Alexandre Petrescu 
>> <alexandre.petrescu@gmail.com> wrote:
>> 
>> Hi,
>> 
>> Before the sanitary situation I was studying an issue at ISO.
>> 
>> The issue is about 64bit MAC addresses and SLAAC.
>> 
>> SLAAC needs a 48bit MAC addresses in order to work, and it can not 
>> work with a 64bit MAC address; (but yes, it can with 64bit IIDs).
> 
> SLACC does not specify the length of the Interface ID, it does not 
> require require 48-bit MAC addresses, and the reason for Modified 
> EUI-64 Format Interface Identifiers in RFC4291 was to support 64bit 
> EUI-64 Identifiers.   We have since moved away from using MAC 
> addresses as Interface IDs.  See RFC 8064.

Bob,

RFC8064 says "this document [...] recommends against embedding stable
link-layer addresses in IPv6 Interface Identifiers".

But a 64bit MAC address could be a random number as well, not
necessarily stable.  Windows randomizes some of its MAC addresses.

That aside, I am not sure how much RFC8064 is clear about the length of
an IID (it refers to RFC7217 '_could_ any len'), neither am I sure how
much is it implemented (linux and freebsd implement random IIDs but of
fixed length).

Alex

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