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From: wrl@wdl1.wdl.loral.com (Bill Lewandowski)
Newsgroups: comp.dcom.sys.cisco
Subject: Re: all of the ethernets interfaces with the same address!?
Message-ID: <1991Apr3.155233.17045@wdl1.wdl.loral.com>
Date: 3 Apr 91 15:52:33 GMT
References: <33874@boulder.Colorado.EDU>
Sender: news@wdl1.wdl.loral.com
Organization: Loral Western Development Labs
Lines: 31

In article <33874@boulder.Colorado.EDU> BILLW@mathom.cisco.com (WilliamChops Westfield) writes:
>
>    In all TCP/IP implementations I know of, all ports on the
>    same machine use the same ethernet (hardware) address.  On
>    initialization, it reads the ROM on the first port it finds,
>    and stores this in all the ports.  
>
>No, this is incorrect.  In fact, I don't know of ANY TCP implementations
>that do this, although it is common in come other protocols (eg XNS).
>In particular, unless you are running some other protocols, cisco routers
>will leave the ethernet address of each ethernet interface at its original
>(and unique) value.
>

Bill, sorry to say but suns have done this to us. Last year we were changing
from network 128.5.0.0 to 137.249.0.0. We wanted to have a machine with
two ethernet interfaces on the same ethernet cable segment so we could have
continous Name Server service (one on each subnet) when the NIC flipped us
and until all the hosts.txt got caught up.

We had problems because the sun on bootup made both ethernet cards the same hardware
address. We had to put a separate hardware address in the "ifconfig" statement for
the second ethernet card in order for us not to get duplicate packets.
(I got a lot of help on this from the "sun-nets" list)

Bill Lewandowski
=========================================================================
-- 
Bill Lewandowski		LORAL Western Development Labs
(408) 473-4362			Internet: wrl@wdl1.wdl.loral.com
FAX: (408) 473-7926		UUCP: wdl1!wrl