Roberto Safora <[log in to unmask]> wrote:
> How do card manufacturers are sure that there is no two cards with the same
> mac address?
> In my LAN when I try to install an e-mail client in one of the Pcs a message
> appears warning there is a conflict with the mac address of other pc.
> TIA

The hardware or MAC address is supposed to be unique. Manufacturers are assigned
"blocks" giving a unique number for the first 3 bytes. In fact, you can
theoretically identify the manufacturer from this number. The other three bytes
are up to the manufacturer to assign as they wish. Perhaps to cut corners, they
reuse addresses assuming for the most part that two identical ones would rarely
end up on the same physical subnet, since the MAC address is not passed beyond a
router.

On some workstations, like Sun Micro, the MAC address for the onboard ethernet
is programmed in a NVRAM chip, and if you know how, you can change it to
anything you wish, for PC NIC cards, I don't know how easy this is, it may not
be possible to change it at all on some. You may have to swap out the NIC to get
a unique address.


--
Russ Poffenberger               Engineering Specialist
Schlumberger Technologies ATE   DOMAIN: [log in to unmask]
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San Jose, Ca. 95134             Voice: (408)586-6718  FAX: (408)586-4675

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