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From: smb@ulysses.UUCP (Steven Bellovin)
Newsgroups: net.lan
Subject: Re: Ethernet addressing - (nf)
Message-ID: <850@ulysses.UUCP>
Date: Wed, 16-May-84 11:54:47 EDT
Article-I.D.: ulysses.850
Posted: Wed May 16 11:54:47 1984
Date-Received: Thu, 17-May-84 03:50:26 EDT
References: <3316@fortune.UUCP>
Organization: AT&T Bell Laboratories, Murray Hill
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	From: rpw3@fortune.UUCP
	Newsgroups: net.lan
	Subject: Re: Ethernet addressing - (nf)
	Message-ID: <3316@fortune.UUCP>
	Date: Tue, 15-May-84 19:05:52 EDT

	Note: If you are going to be a gateway host between two
	Ethernets, make sure your controllers can have the address
	overridden by host software, since it is very important that
	the same absolute physical address appear on both nets. (Usually,
	you go read the default addresses from all the controllers, pick
	one [the smallest? the "first"?], and write that to all of them.)

This applies only if you use the XNS protocols.  Xerox's Internet protocol
calls for a 16-bit network number that does not appear in the Ethernet header,
plus a 48-bit host number that does.  (It may appear elsewhere, but I don't
have my copy of the spec handy.)  This 48-bit number must be the same on all
networks; hence you must override the default board address as Rob describes.
If you use TCP/IP, it doesn't matter, though I suspect that there's some
stuff in 4.2 that would work better if you did.