On Fri, 30 Jul 1999, Doug wrote:
I don't know how this was accomplished, but at my university (using hpux) there was a way to register ip addresses with the hardware address of an individual ethernet card. The only way you could get ethernet access was to register your hardware address. If you tried switching your ethernet cards in your computer, you would have to re-register your new hardware address. So there must be some kind of way to check/supply this hardware address over the network.
Ethernet uses the HW adress to decide whether an packet is for the card or not. This way it works independently from the protocol on top (IPX, IP, Appletalk...). There are ARP-Queries to ask for the HW-Adress when the IP-Adress is known. To recieve packets that are not for your machine, most ethernet adapters can be switched in a so-called promiscous mode. This allows the computer to recieve and send packets with different HW adresses, e. g. bridges often use this. With some cards, its even possible to change builtin HW adress by manipulating the flash ROM. So this method works for most of cases, but is not really safe when the user knows what to do. -- \ markus schaber -- http://www.schabi.de/ -- ICQ# 22042130 / ---------------------------------------------------------- \ Warum umständlich, es geht doch auch kompliziert! / \ (Eva Maria Schaber) --------------------------------