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Date:      Mon, 21 Sep 2009 08:39:35 -0700
From:      "Scott Elgram" <>
To:        "'Steve Bertrand'" <>
Subject:   RE: Help with NAT
Message-ID:  <8CDA12CEBB2F4CD5BAC87320B4B62656@CREDENTALS>
In-Reply-To: <>
References:  <3F3F36886F1E4185AB1EE019FF6DB93D@CREDENTALS> <>

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	Unfortinatly the development and production servers are windows
running IIS.  However, I have tried the following two experiments:
1.) using IIS's logs I am able to see all hits to development and production
servers.  When I visit the development server through the FreeBSD NAT box I
see an entry in the IIS log.  However, on the production server there is no
2.) Using IPFW on the NAT box I logged all traffic in and out of both
interfaces.  The following is what gets recorded for a successful ht to the
development server:
xl1 is the external interface, xl0 is the internal interface, is the comp I was browsing from.
ipfw: 200 Divert 8668 TCP in via
ipfw: 401 Accept TCP in via xl1
ipfw: 401 Accept TCP out via xl0
ipfw: 301 Accept TCP in via xl0
ipfw: 200 Divert 8668 TCP out via xl1
ipfw: 502 Accept TCP out via xl1
And this is what I see when I try the production server:
ipfw: 200 Divert 8668 TCP in via
ipfw: 402 Accept TCP in via xl1
ipfw: 402 Accept TCP out via xl0

At first I thought it might be the production server but I tried another
experiment where I pointed NAT to an IP that is currently working fine
through another NAT box and that didn't work either, so I'm not sure what
the problem is.


-----Original Message-----
[] On Behalf Of Steve Bertrand
Sent: Friday, September 18, 2009 5:18 PM
Subject: Re: Help with NAT

Scott Elgram wrote:
> Hello,
>             I am at my wits end with this one.  I have set up a box to use
> of firewall/nat.  However, during the setup I pointed set net to do a port
> redirect of port 6502 to port 80 of my development web server.  Everything
> worked fine so I deployed my new box onto a live IP and tested it again
> the same redirect to my dev server.  Still, everything works fine so I
> changed /etc/natd.conf to point to my production web server and it won't
> work.  I have tried everything that I can think of to narrow down this
> but I just can't figure it out.  I pointed everything back to my dev
> and it's still working.  I changed the dev servers IP and changed nat to
> point to the new IP and it still works.  It would see that nat will work
> only with my dev server and no other computer.
> Can anyone offer any suggestions, I'm sure I'm missing something basic.

On the production server, after you've got things pointed to it:

# tcpdump -n -i em0 port 80

...where em0 is the interface.

Send a request through from the outside, and verify that you can see the
HTTP request come in to the production box, and go back out again. It
should look like the following. Note that these are v6 addrs not v4, but
the result is the same. In the first packet, 5 -> b6 is request in, and
b6 -> 5 is response back. You 'should' see the same result, but with
your v4 addresses instead.

pearl# tcpdump -n -i em0 port 80

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode

listening on re0, link-type EN10MB (Ethernet), capture size 96 bytes
20:09:52.912361 IP6 2607:f118::5.1752 > 2607:f118::b6.80: S
3408461679:3408461679(0) win 16384 <mss 1440>

20:09:52.912425 IP6 2607:f118::b6.80 > 2607:f118::5.1752: S
1781312333:1781312333(0) ack 3408461680 win 65535 <mss 1440>

...whether you see the packets come in or not, post back with your findings.

Do you perhaps have to 'restart' natd in order to release any sort of


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