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From: stanonik@NPRDC.NAVY.MIL (Ron Stanonik)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Re: Ethernet Address Uniqueness...
Message-ID: <9010121633.AA00795@atlantic.nprdc.navy.mil>
Date: 12 Oct 90 16:33:00 GMT
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Reply-To: stanonik@nprdc.navy.mil
Organization: The Internet
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The 10base5 NI cards in our AT&T 3b2's were all delivered with
the same ethernet address.  This was a big surprise, because we
too had come to expect manufacturer's would assign unique addresses.
The similar ethernet addresses didn't cause any problems because
the IP layer in each machine filtered out only those packets destined
for the local machine.  Everyone ARP'ed to the same ethernet address.  
Sort of like multicasting (unicasting?).  We didn't realize what was
happening until packet tracing to find an unrelated problem.  We've
since found an undocumented command which allows setting the ethernet
address and the machines now all have unique ethernet addresses.

Ron Stanonik
stanonik@nprdc.navy.mil