"illegal" or reserved MAC address ?

Archived from groups: comp.dcom.lans.ethernet (More info?)

Like IP address 10.x.x.x;172.16-31,192.x.x.x,Anyone know what "illegal"
or reserved MAC address which can not use ?
(e.g 0180c2 000001 (1 to f)
Does have any ieee spec. mention it?

Thanks,
sy
3 answers Last reply
More about illegal reserved address
  1. Archived from groups: comp.dcom.lans.ethernet (More info?)

    aaabbb16@hotmail.com (wld) writes:

    >Like IP address 10.x.x.x;172.16-31,192.x.x.x,Anyone know what "illegal"
    >or reserved MAC address which can not use ?

    What do you mean by "can not use"? IP addresses like 10.x.x.x are not
    illegal in any useful sense. They are intended to be used - locally.

    Have a look at http://www.rhyshaden.com/ethernet.htm#Frame - in Chapter 3.2
    you'll find mention of the U/L bit within a MAC address, which determines
    whether a MAC address is universally assigned or locally administered.
    The locally administered addresses, comprising half of the whole address
    space, are morally equivalent to IP layer private addresses from 10.x.x.x,
    192.168.x.x, etc.

    best regards
    Patrick
  2. Archived from groups: comp.dcom.lans.ethernet (More info?)

    mailer-daemon@bof.de (Patrick Schaaf) writes:

    >aaabbb16@hotmail.com (wld) writes:

    >>Like IP address 10.x.x.x;172.16-31,192.x.x.x,Anyone know what "illegal"
    >>or reserved MAC address which can not use ?

    >What do you mean by "can not use"? IP addresses like 10.x.x.x are not
    >illegal in any useful sense. They are intended to be used - locally.

    >Have a look at http://www.rhyshaden.com/ethernet.htm#Frame - in Chapter 3.2
    >you'll find mention of the U/L bit within a MAC address, which determines
    >whether a MAC address is universally assigned or locally administered.

    I see that that reference is confusing. It suggests that the U/L bit were
    only "valid" for some Token Ring addressing format.

    Here's another one, http://www.synapse.de/ban/HTML/P_LAYER2/Eng/P_lay207.html
    Search for U/L in there. But that one is also confusing. They talk about
    every station where the administrator manually configures MAC addresses,
    should set the L bit. Weird, isn't it?

    So, question for the group: is use of the U/L bit (set to L) legal in all
    ordinary Ethernets? Is there a canonical GOOD reference that gives license
    for such usage? Or, is it just "happens to work"?

    best regards
    Patrick
  3. Archived from groups: comp.dcom.lans.ethernet (More info?)

    In article <41298c51$0$13015$9b622d9e@news.freenet.de>,
    mailer-daemon@bof.de (Patrick Schaaf) wrote:

    >
    > So, question for the group: is use of the U/L bit (set to L) legal in all
    > ordinary Ethernets? Is there a canonical GOOD reference that gives license
    > for such usage? Or, is it just "happens to work"?
    >

    Setting the "U/L" bit to "L (local)" is valid, per IEEE 802.3 (about as
    good a "canon" as you are likely to get). All this means is that, for
    the devices so set, responsibility for unique address assignment falls
    on the network administrator, rather than on the manufacturer of the
    device.


    --
    Rich Seifert Networks and Communications Consulting
    21885 Bear Creek Way
    (408) 395-5700 Los Gatos, CA 95033
    (408) 395-1966 FAX

    Send replies to: usenet at richseifert dot com
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