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Date:      Wed, 28 Feb 2001 06:12:28 +0100 (CET)
From:      Tobias Fredriksson <c4@worldclass.jolt.nu>
To:        Alex Rousskov <rousskov@measurement-factory.com>
Cc:        Luigi Rizzo <luigi@info.iet.unipi.it>, freebsd-net@FreeBSD.ORG
Subject:   Re: Quick question about IP aliasing
Message-ID:  <Pine.BSF.4.21.0102280610520.61737-100000@worldclass.jolt.nu>
In-Reply-To: <Pine.BSF.4.10.10102272155120.42355-100000@measurement-factory.com>

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On Tue, 27 Feb 2001, Alex Rousskov wrote:

> On Wed, 28 Feb 2001, Luigi Rizzo wrote:
> 
> > the source of confusion is just the fact that when you ifconfig an
> > interface, you really give two distinct pieces of information:
> >  1. an ip address that the machine recognises as its own
> >  2. an address for a subnet connected to that interface.
> > With aliases you can assign multiple instances of 1 and 2, as long
> > as they are distinct. In your example the subnet address that
> > you try to set with the alias is the same as the one you have
> > already set with the primary ip, so the info is already there and
> > you get the warning/error.
> 
> Luigi,
> 
> 	Can you be more specific please? Is it just a harmless warning
> message or a true error? In other words, will anything break if I use
> a.b.c.2/24 alias on the interface with the a.b.c.1/24 primary address?

No you will be able to bind normaly to a.b.c.1, but i have had the
problems where if i specify anything to bind a.b.c.2 and it has bound on
all ip's aliased on the computer.

> 	I hate to admit, but this thread is very confusing to me --
> several people are claiming opposite things with confidence.
> Unfortunately, I cannot simply ignore the discussion. For benchmarking
> purposes, we routinely use thousands of IP aliases that belong to the
> same subnet on one interface without any known problems. I want to
> know if we are doing something wrong.
> 
> 	I do not care about the ifconfig warning by itself. We do not
> even use ifconfig to manage aliases. I care about the actual run-time
> code that handles the addresses. Could you please clarify whether
> there is anything wrong with using, say, 10.0.0-3.1-250/16 aliases on
> the same interface?
> 
> Thanks a lot,
> 
> Alex.
> 
> 
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