nanog mailing list archives
Re: what about 48 bits?
From: Jonathan Lassoff <jof () thejof com>
Date: Sun, 04 Apr 2010 08:46:17 -0700
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 () 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 () 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. Maybe the NICs shared a single MII/MAC sublayer somehow? I've never borne witness to this though. Re: MAC address exhaustion, if the the second-to-least significant bit in the first byte is 0 (Globally Unique / Individually Assigned bit), then the first three bytes of the MAC should correspond to the manufacturer's "Organizationally Unique Identifier". These are maintained by the IEEE, and they have a list of who's who here: http://standards.ieee.org/regauth/oui/index.shtml I haven't ever programmatically gone through the list, but it looks like a lot of the space is assigned. Cheers, jof
Current thread:
- what about 48 bits? A.B. Jr. (Apr 04)
- Re: what about 48 bits? jim deleskie (Apr 04)
- Re: what about 48 bits? David Andersen (Apr 04)
- Re: what about 48 bits? John Peach (Apr 04)
- Re: what about 48 bits? William Herrin (Apr 04)
- Re: what about 48 bits? Jonathan Lassoff (Apr 04)
- Re: what about 48 bits? Steven Bellovin (Apr 04)
- Re: what about 48 bits? Jim Burwell (Apr 04)
- Re: what about 48 bits? John Peach (Apr 04)
- Re: what about 48 bits? David Andersen (Apr 04)
- Re: what about 48 bits? Mark Andrews (Apr 04)
- Re: what about 48 bits? Mark Smith (Apr 04)
- Re: what about 48 bits? jim deleskie (Apr 04)
- Re: what about 48 bits? Matthew Kaufman (Apr 04)
- Re: what about 48 bits? Scott Howard (Apr 04)
- Re: what about 48 bits? Mark Smith (Apr 04)