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Date:      Thu, 16 Jul 1998 15:22:44 +0300
From:      Ruslan Ermilov <ru@ucb.crimea.ua>
To:        Thomas David Rivers <rivers@dignus.com>, freebsd-hackers@freefall.cdrom.com
Subject:   Re: ipfw rules for exposing an internal machine's port externally?
Message-ID:  <19980716152244.A22669@ucb.crimea.ua>
In-Reply-To: <199807161205.IAA01215@lakes.dignus.com>; from Thomas David Rivers on Thu, Jul 16, 1998 at 08:05:13AM -0400
References:  <199807161205.IAA01215@lakes.dignus.com>

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On Thu, Jul 16, 1998 at 08:05:13AM -0400, Thomas David Rivers wrote:
> 
> I thought I should be able to do this; but it doesn't
> seem to work well.  Perhaps someone knows what I've got wrong here.
> 
> What I have is a machine "X" which is on the external network
> and through which I divert all internal traffic on the 10.0.0.x
> network via ipfw/natd, as in:
> 
>   ipfw add 100 divert 32000 ip from any to any via sl0
> 
> 
> However, I have an internal machine (10.0.0.10) that's set up
> to do telnet connections on a different port (e.g. port #PPPP in 
> the following example.)
> 
> I would like to make those connections available externally.
> 
> So - I've got added:
> 
>    ipfw add 50 pass log tcp from any PPPP to 10.0.0.10 PPPP
>    ipfw add 50 pass log udp from any PPPP to 10.0.0.10 PPPP
> 
> But, if I telnet to the gateway machine at port PPPP as in:
> 	telnet gateway PPPP
> all I get is:
> 	Trying x.x.x.x...
> 	telnet: Unable to connect to remote host: Connection refused
> 
> 
> If I, however, telnet on the internal network to 10.0.0.10 PPPP
> I get connected just fine.
> 
> 
> 
> Has anyone done this before?  That is, map a particular port number
> on one machine to a different one?  And, use that with divert to
> make a service on an internal machine externally visible?  If so, how?
> 

You're missing redirect natd rule, it seems to me.
Add the following line in natd config file on "X":

redirect_port	tcp	10.0.0.10:PPPP PPPP

This will tell natd to redirect X:PPPP connection to 10.0.0.10:PPPP.

HTH and regards,
-- 
Ruslan Ermilov		Sysadmin and DBA of the
ru@ucb.crimea.ua	United Commercial Bank
+380.652.247.647	Simferopol, Ukraine

http://www.FreeBSD.org	The Power To Serve
http://www.oracle.com	Enabling The Information Age

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