[AusNOG] Internal use MAC addresses

[Geordie Guy]

Thanks folks.
On 24/02/2013 8:26 AM, "Mark Smith" <markzzzsmith at yahoo.com.au> wrote:

>
> >________________________________
> > From: Wade Roberts <ausnog at acquired-taste.net>
> >To: Keith Sinclair <kcsinclair at gmail.com>
> >Cc: "ausnog at lists.ausnog.net" <ausnog at lists.ausnog.net>
> >Sent: Saturday, 23 February 2013 10:08 PM
> >Subject: Re: [AusNOG] Internal use MAC addresses
> >
> >
> >Not quite, setting the 'next-to-least-significant-bit of first octet of
> OUI', or the 7th bit, to 1 would make 02-00-00 the simplest example of this
> rule.
> >
>
> Another way to look at it is that in hexadecimal, 0x02 needs to be present
> in the first octet. If you have a hexadecimal to binary calculator, convert
> the first octet from hexadecimal to binary and then look for a 1 in the Y
> position - xxxx xxYx.
>
> For those interested in the origins of why MAC addresses are 48 bits and
> why they were intended to be globally unique, have a read of the following
> paper:
>
> "48-bit Absolute Internet and Ethernet Host Numbers"
> http://ethernethistory.typepad.com/papers/HostNumbers.pdf
>
>
> Interestingly, they were originally intended to be globally unique host
> rather than interface identifiers, and if a host had multiple interfaces,
> the same MAC address was intended to be used on all of them. That would
> have precluded the attachment of two of the host's interfaces to the same
> link. I think the convention of a MAC address being assigned to an
> interface probably came about because when a host didn't already have a MAC
> address, it was easier for a network card manufacturer to put one on some
> ROM/EEPROM on the card, and then for manufacturing simplicity, do it on all
> cards rather than making it optional.
>
> For example, the following shows that SUN originally adopted the same MAC
> address on all interfaces model and made it the default:
>
>
> http://docs.oracle.com/cd/E19963-01/html/821-1458/geyqe.html#eyprp#scrolltoc
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