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Date:      Mon, 03 Apr 2000 10:44:18 +0100
From:      Brian Somers <brian@Awfulhak.org>
To:        Luigi Rizzo <luigi@info.iet.unipi.it>
Cc:        Brian Somers <brian@Awfulhak.org>, Brendan Kosowski <brendan@bmk.com.au>, FreeBSD Networking <freebsd-net@FreeBSD.ORG>, brian@hak.lan.Awfulhak.org, brian@hak.lan.Awfulhak.org
Subject:   Re: natd problem 
Message-ID:  <200004030944.KAA01499@hak.lan.Awfulhak.org>
In-Reply-To: Message from Luigi Rizzo <luigi@info.iet.unipi.it>  of "Mon, 03 Apr 2000 10:38:40 %2B0200." <200004030838.KAA56450@info.iet.unipi.it> 

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If you've got a spare IP number, I prefer this:

        $fwcmd add 101 divert natd all from 172.16.0.0/12 to any out via fxp0
        $fwcmd add 102 divert natd all from any to $natd_interface in via fxp0

Here, natd_interface is my spare IP number (which has been ifconfig'd 
as an alias on fxp0) and 172.16.0.0/12 is my internal network.

All connections going out get the default (first) IP number on fxp0 
and natd doesn't even get to see them.  You may also want to add

        $fwcmd add 101 divert natd all from $natd_interface to any out via fxp0

just in case someone wants to use something like datapipe (ports) to 
specifically make their from address the same as $natd_interface.

> > The problem here is that the reply packets are going direct and 
> > aren't getting de-aliased by natd - natd doesn't even get to see them.
> 
> speaking of this... the usual suggestion for setting NATD is to
> config the firewall as
> 
> 	ipfw -q flush
> 	ipfw add 100 divert natd ip from any to any via $natd_interface
> 	ipfw add 200 allow ip from any to any
> 
> but this puts a lot of load on the machine acting as natd daemon,
> as all local traffic is also passed to the daemon where it is not
> subject to any translation.
> In some cases this is quite a problem e.g. when you put
> all sorts of services on the same machine doing natd.
> 
> Does anyone have a more accurate way to pass interesting packets
> to the daemon ?
> 
> I could probably come up with something but i'd rather avoid
> duplicating work already done.
> 
> 	cheers
> 	luigi
> 

-- 
Brian <brian@Awfulhak.org>                        <brian@[uk.]FreeBSD.org>
      <http://www.Awfulhak.org>;                   <brian@[uk.]OpenBSD.org>
Don't _EVER_ lose your sense of humour !




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