what about 48 bits?

John Peach john-nanog at johnpeach.com
Sun Apr 4 16:56:07 CDT 2010


On Sun, 04 Apr 2010 14:48:38 -0700
Jim Burwell <jimb at jsbc.cc> wrote:

> On 4/4/2010 08:46, Jonathan Lassoff wrote:
> > Excerpts from John Peach's message of Sun Apr 04 08:17:28 -0700 2010:
> >   
> >> On Sun, 4 Apr 2010 11:10:56 -0400
> >> David Andersen <dga at cs.cmu.edu> wrote:
> >>
> >>     
> >>> There are some classical cases of assigning the same MAC address to every machine in a batch, resetting the counter used to number them, etc.;  unless shown otherwise, these are likely to be errors, not accidental collisions.
> >>>
> >>>   -Dave
> >>>
> >>> On Apr 4, 2010, at 10:57 AM, jim deleskie wrote:
> >>>
> >>>       
> >>>> I've seen duplicate addresses in the wild in the past, I assume there
> >>>> 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 at gmail.com> wrote:
> >>>>         
> >>>>> 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 be. Or it
> >>>>> is assumed that mac addresses are being widely reused throughout the world?
> >>>>> All those low cost switches and wifi adapters DO use unique mac addresses?
> >>>>>
> >>>>>           
> >> Sun, for one, used to assign the same MAC address to every NIC in the
> >> same box.
> >>     
> > I could see how that *could* work as long as each interface connected to
> > a different LAN.
> >   
> 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".

You can set the MAC address to whatever you want in Solaris, using
ifconfig and local-mac-address was (is) the PROM variable.


-- 
John




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