On Jun 6, 2012, at 1:02 PM, Steve Clark wrote:

On 06/06/2012 03:05 PM, Owen DeLong wrote:

...

It is because of IEEE EUI-64 standard.

It was believed at the time of IPv6 development that EUI-48 would run out of numbers and IEEE had proposed going to EUI-64. While IEEE still hasn't quite made that change (though Firewire does appear to use EUI-64 already), it will likely occur prior to the EOL for IPv6.

There is a simple algorithm used by IEEE for mapping EUI-48 onto the EUI-64 space.

The 0x02 bit of the first octet of an EUI-64 address is an L-Flag, indicating that the address was locally generated (if it is a 1) vs. IEEE/vendor assigned (if it is a 0).

The mapping process takes the EUI-48 address XX:YY:ZZ:RR:SS:TT and maps it as follows:

let AA = XX xor 0x02.

AAYY:ZZff:feRR:SSTT

ff:fe above is literal.

IPv6 was originally going to be a 32-bit address space, but, the developers

did you mean "originally going to be a 64-bit address space"...

Uh, yeah... Sorry... Brain fart. Originally a 64-bit address space. Owen