On Apr 4, 2010, at 11:46 17AM, 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 <d...@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. <skan...@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.
There was a socketed ROM IC with the *machine's* MAC address on the motherboard, way back when. If your motherboard needed replacing, the tech would move that IC to the replacement. Why was this done? The reason was simple: compatibility with other stacks. Remember that circa 1988-1990, it was not obvious that TCP/IP was going to be the winner. --Steve Bellovin, http://www.cs.columbia.edu/~smb