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Ethernet MAC address

Discussion in 'Electronic Design' started by Pszemol, Sep 17, 2003.

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  1. Pszemol

    Pszemol Guest

    When a company designs a device with Ethernet it needs to programm MAC in it.
    I know IEEE assigns MAC numbers and charges for this fee.
    I know also the meaning of bit 46th means:
    =0 - address given by IEEE
    =1 - address NOT given by IEEE
    Does it mean there is a legal way to not go to IEEE for that number and
    program the Ethernet MAC address with a random number with 46th bit set?
    I know I would risk my address being not unique, but this is very small
    volume production and it would not be a big problem. I am more concern with
    a legal side of this issue. Is there a legal force to go to IEEE for MAC?
    Anybody here experienced in manufacturing Ethernet device?
  2. There is no guaranty that MACs will be unique anyway. It only has to
    be unique on the subnet. Many Ethernet cards allow the end-user to set
    the MAC (in case of collision). If your device is a home-brew, pick any
    MAC. If you're making a product, take out a block of numbers.
  3. Ian Stirling

    Ian Stirling Guest

    Ask the IEEE?

    To completely ensure non-collision, you could buy a crate of whatever
    network card is cheapest, and copy the MACs.
  4. Dana Raymond

    Dana Raymond Guest

    I've designed products where we didn't bother to register MAC addresses.
    However, each installation was doen by an Engineer and involved small sized

    I wouldn't worry about it unless you are selling mass market consumer

    Dana Frank Raymond
  5. Pszemol

    Pszemol Guest

    Do you know what is the legal status if this issue?

    My device will be installed in very small subnets
    (5-6 devices + router) and will be sold with the
    installation done by the professional. It will not
    be sold on the shelf in the supermarket ;-)
  6. Dana Raymond

    Dana Raymond Guest

    No, I can't advise you on the legality for obvious reasons.
    All I can contribute is observation.
    If you are really concerned, I would contact the authority that provides MAC
    address blocks.
    I spend some time just now trying to find anything that says the IEEE can do
    anything to you if you do not register for a MAC address block. However, you
    could be misrepresenting your product as ethernet compliant, or something
    like that, if you don't follow the rules. I suspect product liability as
    opposed to enforcement may be your real concern.

    Sorry I couldn't be more definitive.
    Dana Frank Raymond
  7. Ian Stirling

    Ian Stirling Guest

    There is supposed to be a guarantee.
    That's the point of buying number blocks from the IEEE.
    They assign you a block, and then you assign unique MACs from this pool, until
    you need another one.

    Nearly all ethernet cards take a packet that the ethernet stack has built,
    and transmit it without touching the MAC.
    The driver reads the MAC from the card, and tells the ethernet stack, which
    then builds the packets.

    The ability to set MACs is more for network admin.
  8. Uns Lider

    Uns Lider Guest

    You're going to sell it? Surely you can spend $550 and get an Individual
    Address Block. How do you think your customers would react if they found
    out you were using a phony MAC address instead?

    -- uns
  9. Pszemol

    Pszemol Guest

    Where did you get $550? I read on IEEE site it costs over $1600. $550 sounds much better! :)

    If you are very small company and make a small series of devices
    almost manufacturing them, then the share of $1600 for each device
    is substantial to think about how to avoid paying this fee.

    Especialy one bit of MAC address is telling you it is or it is not
    assigned by IEEE. What is the purpose of this bit? When is it used?
  10. Joel Kolstad

    Joel Kolstad Guest

    Yes, although it will probably cost you more than $1600 to fix if you ever
    do run into the suddenly bizarre problem whereby your customer just so
    happens to have another machine with the same MAC ID. (Especially if the
    customers add more machines to their subnet after you're long gone... since
    the OP suggested that 'engineers' would be installing the devices initially,
    and hopefully would be able to check for MAC collisions.)

    All the same, I can appreciate that $1600 is a lot for a small company. PCI
    has a nice solution to this problem (or at least a somewhat related one) in
    that they provide both a vendor and device ID field as well as a sub-vendor
    and sub-device ID field in their configuratoin space ROMs. At the last
    company I worked for, we were using a PLX Technologies 9054 PCI interface
    IC, and if PCI vendor IDs were free, I'm sure we would have changed it to
    point at us rather than PLX. As it was, we didn't want to pony up the
    some-thousands of bucks to do this, so we just changed the sub-vendor ID to
    our own (which PLX then registered for us for free in their internal
    database) and left the vendor ID as PLX. (And Microsoft now says we
    shouldn't have ever thought about changing the vendor ID field anyway unless
    it really was our interface IC and not PLX's, so there...)

    With Ethernet, it does seem as though the 'non-IEEE' bit was meant to be the
    solution to this problem? So that someone else can sit around registering
    MAC addresses? I realize that the IEEE performs worthy activities (I am a
    member) and the rationale behind such a high registration fee, but it sure
    seems like they could benefit from a little competition -- look at how much
    DNS registration fees dropped after the Internic had to compete!

    ---Joel Kolstad
  11. Any chance that one can buy a few MACs from another company? Or go in
    with a few smaller developers and split a $1600 block of addresses?
  12. I know I would risk my address being not unique, but this is very small
    I dunno about the legal side, but for very small volume production you
    could get yourself a bunch of (second hand) ethernet cards, use their
    ethernet numbers, and smash the cards.

    Wouter van Ooijen

    -- ------------------------------------
    PICmicro chips, programmers, consulting
  13. Dana Raymond

    Dana Raymond Guest

    About buying MAC addresses from someone else... I came across a site where
    they were selling blocks of 256 from their original 4096. The site posted a
    series of letters between them and IEEE where IEEE says the addresses cannot
    be resold. The site's position was that nothing was ever said about that,
    but IEEE insisted. In the end IEEE purchased the 4096 block back.

    IEEE's position is that the 4096 block is for a manufacturer's own products,

    Dana Frank Raymond
  14. Joel Kolstad

    Joel Kolstad Guest

    That definitely drops my opinion of the IEEE a few notches. :-(
  15. Not that I'd recommend this,
    but you could probably buy an ancient ethernet card,
    say a 3Com 3C501, take it's Mac address, and increment up from there.

    There were probably 100,000 of those cards made, nobody's going to
    still be using them, particularly on a new subnet.

    Or better yet, get a PDP-11 ethernet card Mac address. Darn few PDP-11's
    around anymore, and I doubt if DEC nee Compaq is going to care.
  16. Ian Stirling

    Ian Stirling Guest

    "My product is a sticky label with a MAC address on it."
  17. Uns Lider

    Uns Lider Guest

  18. but you could probably buy an ancient ethernet card,
    I would not trust a procedure that is not robuust against someone else
    following the same procedure :(

    Better take the cards address, smash the card, and take a next card
    for the next address.

    Wouter van Ooijen

    -- ------------------------------------
    PICmicro chips, programmers, consulting
  19. Zak

    Zak Guest

    I think an end user is supposed to be able to assign these at will. A
    pre-bought device using these may not be allowed.

    But what about going to a scrapyard, collecting old network cards and
    using those MACs? They often have the MAC printed on them...

    But then you could be misrepresenting your device as the MAC is tied to
    the vendor.

    FWIW there are PCI network cards being sold that do not have a MAC at
    all. The customer has to select a MAC in the Windows driver for the
    thing. If he doesn't, it is all zeroes. Not Good.


  20. I should have amplified my answer for those who don't know about the 3C501
    or other ancient cards:

    The 3C501 was a disaster in many ways-- it would drop every-other packet in
    many cases,
    it only accepted AUI or BNC cables. Most everybody stopped using these
    cards by 1995.

    I doubt if anybody today is building networks with AUI or BNC cables, 10mbps
    only, so that precludes the presence of those old cards.

    So I suspect 3C501 numbers would be reasonably safe to use.

    NOT that I'd recommend anything along thee lines...
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