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Date:      Wed, 15 Mar 1995 01:03:47 -0500 (EST)
From:      Denis Fortin <fortin@zap.zap.qc.ca>
To:        ugen@netvision.net.il (Ugen J.S.Antsilevich)
Cc:        jg@euronet.nl, questions@FreeBSD.org
Subject:   Re: Routing and Ethernet
Message-ID:  <199503150603.BAA02907@zap.zap.qc.ca>
In-Reply-To: <Chameleon.950314124823.ugen@ugen.NetManage.co.il> from "Ugen J.S.Antsilevich" at Mar 14, 95 05:46:54 am

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> >You cannot have two physically different wires that have the same network
> >(193.78.175.*) on them.  This is a TCP/IP issue, not a FreeBSD problem.
> 
> Wrong! You can and how...as a simple example i have on my machine two adresses
> ep0 is 194.90.1.15 and ed0 is 194.90.1.18...

Hmmm.  I could see that this might be possible if both cards are on the
same physical Ethernet (though I can't really see how that would be useful 
unless you've got a slow ethernet card).  

I cannot see how it would make sense if both cards are on different
Ethernet segments and have the same netmask (0xffffff00)!!! In that
case, there would be no way of determining through which interface
(and hence on which wire) a packet destined to 194.90.1.17 would go.

> If you can have two different IP's for same interface you even better can 
> have different IP's for different interfaces no matter on which network...

I'm not sure I follow this.  If I understand right, it seems to violate
half a dozen RFCs and create difficult routing problems.

With most TCP/IP implementations I've seen, it is possible to build 
fully working but incorrect network configurations.  Sometimes it may
even (appear to) be useful to do this.
-- 
Denis Fortin                                                    fortin@acm.org
DMR Group Inc, (514) 877-3301                        These opinions are my own



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