On Jan 1, 2011, at 11:33 24PM, Mark Smith wrote: > On Sat, 01 Jan 2011 20:59:16 -0700 > Brielle Bruns <br...@2mbit.com> wrote: > >> On 1/1/11 8:33 PM, Graham Wooden wrote: >>> So here is the interesting part... Both servers are HP Proliant DL380 G4s, >>> and both of their NIC1 and NIC2 MACs addresses are exactly the same. Not >>> spoofd and the OS drivers are not mucking with them ... They¹re burned-in >>> I triple checked them in their respective BIOS screen. I acquired these two >>> machines at different times and both were from the grey market. The ³What >>> the ...² is sitting fresh in my mind ... How can this be? >> >> >> From the same grey market supplier? >> >> I know HP has a disc they put out which updates all the firmware/bios in >> a specific server model, its not too far fetched that a vendor might >> have a modified version that also either purposely or accidentally >> changes the MAC address. Off the top of my head, I'm not sure where the >> MAC is stored - maybe an eeprom or a portion of the bios flash. Or, it >> could be botched flashing that blew away the portion of memory where >> that was stored and the system defaulted to a built in value. >> >> Excellent example is, IIRC, the older sparc stuff, where the ethernet >> cards didn't have MAC addresses as part of the card, but were stored in >> non-volatile or battery backed memory. > > This was actually the intended way to use "MAC" addresses, to used as > host addresses rather than as individual interface addresses, according > to the following paper - > > "48-bit Absolute Internet and Ethernet Host Numbers" > Yogan K. Dalal and Robert S. Printis, July 1981 > http://ethernethistory.typepad.com/papers/HostNumbers.pdf
Yup. > > That paper also discusses why 48 bits were chosen as the size, despite > "Ethernet systems" being limited to 1024 hosts. > > I think things evolved into MAC per NIC because when add-in NICs > were invented there wasn't any appropriate non-volatile storage on the > host to store the address. > On really old Sun gear, the MAC address was stored on a separate ROM chip; if the motherboard was replaced, you'd just move the ROM chip to the new board. I'm not sure what you mean, though, when you say "when add-in NICs were invented" -- the Ethernet cards I used in 1982 plugged into Unibus slots on our VAXen, so that goes back quite a ways... --Steve Bellovin, http://www.cs.columbia.edu/~smb