On 03.05.2002 at 05:36:46, Rich Smrcina <[EMAIL PROTECTED]> wrote: > Could the virtual MAC have some element or elements of the CPUID in it, then > a CP maintained counter for uniqueness?
That's a good start, but unfortunately 6 hex digits for the 'manufacturer ID' and six digits for the serial number already fills up our 12 hex digit MAC address, and we're still not unique since different machine types will reuse serial numbers... Maybe IBM could register a 'block' of manufacturer IDs so that the serial number could be pushed up into the manufacturer field, making more room for a locally-maintained counter. Alternatively, using Locally Administered Address (LAA) instead of Universally Administered Address (UAA) puts the onus of uniqueness back onto the customer, and potentially frees up more of the 48-bit field for local use (in theory, an LAA is supposed to start with X'4000', but generally as long as the first two bits are '01' it's recognised as an LAA -- this for token-ring, however, so rules may be different for ethernet). I *know* that TCP/IP has eliminated the need for LAAs (thanks to ARP), and that the overhead of administering LAAs has been largely forgotten by most shops, but it might offer a more flexible solution in this scenario. Cheers, Vic Cross -- Vic Cross MACS mailto:[EMAIL PROTECTED] Networking, Linux, on zSeries and S/390
