Hello all...

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.)

With the way technology moves on, I got to wondering if there is ever a time
when a network card's MAC address is considered to be "free" because the
hardware that it was originally assigned to should be long since out of use?

(Why am I wondering about this? Because I run a lot of older networking gear
(much of it token ring) and it seemed like something to think about.)

William

"William R. Walsh" m
wrote in message news:buc3h.1051173$084.982789@attbi_s22...
Hello all...

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.)

With the way technology moves on, I got to wondering if there is ever a
time
when a network card's MAC address is considered to be "free" because the
hardware that it was originally assigned to should be long since out of
use?

(Why am I wondering about this? Because I run a lot of older networking
gear
(much of it token ring) and it seemed like something to think about.)

William

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

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.

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.

--
Joop van der Velden -

"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.

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.


Right. Was in a hurry. Point is, you'd have to be more unlucky than someone
who wins the lottery is lucky.

On Sun, 05 Nov 2006 04:19:34 GMT, "T Shadow"
put finger to keyboard and composed:

"William R. Walsh" m
wrote in message news:buc3h.1051173$084.982789@attbi_s22...
Hello all...

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.)

With the way technology moves on, I got to wondering if there is ever a
time
when a network card's MAC address is considered to be "free" because the
hardware that it was originally assigned to should be long since out of
use?

(Why am I wondering about this? Because I run a lot of older networking
gear
(much of it token ring) and it seemed like something to think about.)

William

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

How many addresses are in a manufacturer's block?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

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 -

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:

"Franc Zabkar" wrote in message
...
On Sun, 05 Nov 2006 04:19:34 GMT, "T Shadow"
put finger to keyboard and composed:

"William R. Walsh" m
wrote in message news:buc3h.1051173$084.982789@attbi_s22...
Hello all...

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.)

With the way technology moves on, I got to wondering if there is ever a
time
when a network card's MAC address is considered to be "free" because the
hardware that it was originally assigned to should be long since out of
use?

(Why am I wondering about this? Because I run a lot of older networking
gear
(much of it token ring) and it seemed like something to think about.)

William

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

How many addresses are in a manufacturer's block?
- Franc Zabkar

More than I remembered. 24bit. Still leaves 16 million + numbers.
Have no reason to think a manufacturer can only have one number set.
Year estimated to run out of numbers, 2100.

Bob Shuman wrote:

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.

Of the first 24 bits, there is 1 bit reserved for broadcast/multicast
addresses and 1 bit is reserved for locally assigned ethernet addresses.

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)

We are talking Ethernet addresses here. Not IP addresses.

Ethernet addresses can be self assigned and administered. On every
ethernet card the burned-in address can be changed into whatever you
want it to be. If you do you should set the LAA bit.
(Locally Administered Address)

http://www.myne****chman.com/pckidiot/chap04.htm

--
Joop van der Velden -