[124757] in North American Network Operators' Group
Re: what about 48 bits?
daemon@ATHENA.MIT.EDU (Jim Burwell)
Sun Apr 4 17:49:20 2010
Date: Sun, 04 Apr 2010 14:48:38 -0700
From: Jim Burwell <jimb@jsbc.cc>
To: nanog@nanog.org
In-Reply-To: <1270395578-sup-3974@sfo.thejof.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 4/4/2010 08:46, Jonathan Lassoff wrote:
> Excerpts from John Peach's message of Sun Apr 04 08:17:28 -0700 2010:
> =20
>> On Sun, 4 Apr 2010 11:10:56 -0400
>> David Andersen <dga@cs.cmu.edu> wrote:
>>
>> =20
>>> There are some classical cases of assigning the same MAC address to e=
very machine in a batch, resetting the counter used to number them, etc.;=
unless shown otherwise, these are likely to be errors, not accidental c=
ollisions.
>>>
>>> -Dave
>>>
>>> On Apr 4, 2010, at 10:57 AM, jim deleskie wrote:
>>>
>>> =20
>>>> I've seen duplicate addresses in the wild in the past, I assume ther=
e
>>>> is some amount of reuse, even though they are suppose to be unique.
>>>>
>>>> -jim
>>>>
>>>> On Sun, Apr 4, 2010 at 11:53 AM, A.B. Jr. <skandor@gmail.com> wrote:=
>>>> =20
>>>>> Hi,
>>>>>
>>>>> Lots of traffic recently about 64 bits being too short or too long.=
>>>>>
>>>>> What about mac addresses? Aren't they close to exhaustion? Should b=
e. Or it
>>>>> is assumed that mac addresses are being widely reused throughout th=
e world?
>>>>> All those low cost switches and wifi adapters DO use unique mac add=
resses?
>>>>>
>>>>> =20
>> Sun, for one, used to assign the same MAC address to every NIC in the
>> same box.
>> =20
> I could see how that *could* work as long as each interface connected t=
o
> a different LAN.
> =20
That was a logic Sun used. Every NIC would be connected to a different
subnet, so duplicate MACs shouldn't be a problem. For the most part
this worked, but some situations required a unique MAC per NIC, and Sun
had a bit you could flip to turn this on. I believe it was an OpenBoot
prom variable called "local-mac-address?" which you'd set to true if you
wanted it to use each NICs MAC instead of the "system MAC".
-Jim
