[124796] in North American Network Operators' Group
Re: what about 48 bits?
daemon@ATHENA.MIT.EDU (Kevin Oberman)
Mon Apr 5 01:27:39 2010
To: Larry Sheldon <LarrySheldon@cox.net>
In-reply-to: Your message of "Sun, 04 Apr 2010 23:30:42 CDT."
<4BB96772.3090102@cox.net>
Date: Sun, 04 Apr 2010 22:26:52 -0700
From: "Kevin Oberman" <oberman@es.net>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
> Date: Sun, 04 Apr 2010 23:30:42 -0500
> From: Larry Sheldon <LarrySheldon@cox.net>
>
> I keep seeing mention here of the "permanent" MAC address.
>
> Really? Permanent?
>
> Been a long time, but it seems like one of the fun things about having
> DECNet-phase IV on the network was its propensity for changing the MAC
> address to be the DECNet address.
>
> And it seems like the HP-UX machines (among others) could write what
> every they wanted to as addresses.
Almost every system can re-write the MAC address. It's in the original
802.3 and DIX (Blue Book) Ethernet standards. I have not run into a
system in some time that lacked this capability. Works on Windows,
MacOS, Linux, and BSD.
That said, all 802.3 devices are expected to have a permanent MAC
address in ROM. At initialization time, that address is always used
until software can program in the new address. Made MOP-DL booting
(DECnet equivalent of bootp) interesting.
--
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman@es.net Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751
