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From: stewart@XYPLEX.COM (Bob Stewart)
Newsgroups: comp.protocols.tcp-ip
Subject: Reply to Ethernet Address Uniqueness...
Message-ID: <9010051859.AA07361@xap>
Date: 5 Oct 90 15:59:38 GMT
References: <5A0A050B012801FE-MTAEMR1*fillmore@emrcan>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 18

>In the DEC VAX environment the unique Ethernet address on each board is
>overridden by DECNET when it starts to use that board.  The address is set
>to four bytes of a constant value plus two bytes which contain the DECNET
>area and node numbers.  Lots of opportunity for duplication!
>Does anyone know why DEC chose this scheme?
>
>  - Bob Fillmore     FILLMORE@EMRCAN.BITNET

I believe it was to keep down the size of routing tables.  Since the Ethernet
address can be calculated from the DECnet address, you don't have to keep a
48-bit MAC address in your mapping from Network layer to Data Link layer.

	Bob

-----------
Bob Stewart (rlstewart@eng.xyplex.com)
Xyplex, Boxborough, Massachusetts
(508) 264-9900