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Date:      Wed, 10 Oct 2001 05:20:18 -0700
From:      "Ted Mittelstaedt" <tedm@toybox.placo.com>
To:        <irado@nettaxi.com>, <freebsd-questions@freebsd.org>
Subject:   RE: routed tutorial
Message-ID:  <000601c15185$ec6c3820$1401a8c0@tedm.placo.com>
In-Reply-To: <200110091200.f99C0V406813@mail10.bigmailbox.com>

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>-----Original Message-----
>From: irado@nettaxi.com [mailto:irado@nettaxi.com]
>Sent: Tuesday, October 09, 2001 5:01 AM
>To: freebsd-questions@freebsd.org
>Cc: tedm@toybox.placo.com
>Subject: RE: routed tutorial
>
>
>maybe you are right. What do I need is what I mentioned previously:
>3 ADSL fixed ip-address (public) must react as a single link,

not possible.

 the
>internal (192.168..) lan being nat'ed to the first available one -
>no 'mandatory' pathway. And I really need some light as I am really
>blind on 'where' I can get advice. Any hint, url, will be of great help.
>

you won't find anything because nobody has anything like this working.

Look at it this way.  Suppose you set up a box like you describe.  The
interfaces are numbered:

outside:

(1) 205.205.2.4
(2) 45.67.2.4
(3) 64.3.2.1

inside:

192.168.1.1

The NAT process in the router will translate the traffic coming from the
inside to - what?  Well, let's say that it translates it to 205.205.2.4

The NAT then routes the translated packet out - what?  Well, the only
interface
it can do it to is 1 - because interface 2 and 3 will only accept packets from
45.67.2.4 and 64.3.2.1 respectively.

Now, the packet reaches it's destination and a response is sent back to
205.205.2.4.  Well, the INTERNET will route the response back to interface
1, NOT interface 2 or 3.

Thus, if the NAT uses 205.205.2.4 as it's translated IP number then ALL the
traffic will pass through interface 1.

If it uses 45.67.2.4 as it's translated IP number then ALL the traffic will
pass
though 2, and so forth.

Your problem here is that when your dreaming this scheme up your only looking
at
the Internet from the perspective of your own network - sending traffic out to
the Internet.  Your forgettting that you must also look at your own network
from the perspective of the Internet.

You can control whatever interface you want to send all your traffic out on -
but
you cannot control the interface that the Internet chooses to send the
response
traffic back to - at least not without your own AS and without running BGP.


Ted Mittelstaedt                                       tedm@toybox.placo.com
Author of:                           The FreeBSD Corporate Networker's Guide
Book website:                          http://www.freebsd-corp-net-guide.com


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