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From: rpw3@amdcad.UUCP (Rob Warnock)
Newsgroups: comp.dcom.lans
Subject: Re: Ethernet Physical Address
Message-ID: <13777@amdcad.UUCP>
Date: Sun, 16-Nov-86 13:16:26 EST
Article-I.D.: amdcad.13777
Posted: Sun Nov 16 13:16:26 1986
Date-Received: Sun, 16-Nov-86 20:33:34 EST
References: <939@ssc-vax.UUCP>
Distribution: na
Organization: [Consultant] San Mateo, CA
Lines: 25
Summary: Changing Ethernet address IS required (sometimes)

+---------------
| Digging a bit further, I note that our Interlan ethernet boards also have the 
| capability for over-riding the built-in physical address.
| 
| Would any one care to shed some light on why this is necessary or desirable?
| Does it not tend to increase the risk of an address conflict on a large,
| multi-protocol, mult-vendor net?
+---------------

Note that an Xerox XNS node is required to have the *SAME* Ethernet address
on *ALL* nets that it is connected to. (In XNS the Ethernet address *is* the
host address. In TCP/IP language, the physical address *is* the IP address).
Since the two (or more) controllers used in that situation will come with
more than one address, all but one of them has to change. Typically, you
simply pick the largest (or smallest) address of any of the controllers,
and set that address into all of them. There is no conflict, since you own
all of those addresses anyway.


Rob Warnock
Systems Architecture Consultant

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