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Baron

Bob Shuman wrote:

See comments in line below.

"Joop van der Velden" wrote in message
...
T Shadow wrote:

It's my understanding that makers of network cards buy up blocks
of MAC addresses to use on their finished cards. (I also
understand that some NIC
makers have seemingly reused the block they purchased with
the--sometimes
mistaken--belief that no two adapters would ever "see" one another
on the
same network segment.)

MAC address is 6 hexadecimal numbers. Do the math and report back.

Well, in fact it's 12 hex numbers ;-) Or 48 bits.
It's more a potential problem of lack of administration at the
manufacterers side, or errors made by programmers of network drivers.

48 bits = 12 4 bit hexadecimal words. The forst 24 bits are reserved
to
uniquely identify the manufacturer. The last 24 bits are for a unique
serial number. As such, each "manufacturer" can produce 16,777,215
(2**24 -1) unique serial numbers. If these get used up, then the
manufacturer can request/designate another 24 bit prefix and double
their MAC address space.

If you really want to keep things in your own hand, start using self
assigned network addresses and do the administration yourself.
Half of the total ethernet address space is reserved for locally
assigned addresses.

Could you please explain this last statement that "Half of the total
Ethernet address space is reserved for locally assigned addresses?" I
ask since if this was IPV4 you were referencing, then the only
"private" (local) addresses are in the range 10.0.0.0/8 (maximum
16,777,214 adresses), 172.16.0.0/12 (max 1,048,574 addresses), and
192.168.0.0/16 (max 65,534
addresses). This is a maximum total of 17,891,322 unique addresses
out of the 4,294,967,296 (2**32) total addresses - about 4% of the
total!

Bob

--
Joop van der Velden -

The only correlation between the MAC address and an IP address is
whatever IP you give to it. A network card will have an assigned MAC
address that you can choose to ignore or not, in favour of an IP.

--
Baron: