[X4U] MAC address vs ? Ethernet Address ?

[Richard Gilmore]

On 3/8/05 6:11 PM, "Craig A. Finseth" <fin at finseth.com> wrote:

> ...
>> Again, there is no such thing as "_the_ true MAC address of the machine".
>> .........
>> 
>> Oh, yeah.  All of these can be changed under software control.
>> 
>> Craig
> 
>    So these numbers can be faked through software? They are not "burned" into
>    the ethernet card itself?
> 
> Both.  The interface has factory-assigned default numbers that are unique.
> However, the software can change them.

So the card itself is not hard wired with a number?
 
> This is an integral part of the Ethernet interface specification and
> some (ok, now obsolete) networking protocols rely on it (e.g.,
> DECnet).
> 
> And "faked" is not the correct term: since the _only_ important
> property of them is that they are unique in a contiguous layer 2
> network and the value is _never_ supposed to be significant, it is
> perfectly ok to make up whatever numbers you want: there is no meaning
> to fake.
> 
> Craig

Could you explain this a little more? I'm not that well versed in computer
terminology. 

What's a contiguous layer 2 network?