iptables help please

Willem van der Walt wvdwalt at csir.co.za
Thu Mar 22 03:52:45 EDT 2007


I have not done this, but if what you have done below does not work, I 
would replace the -i lo with -s 127.0.0.1
and see if it helps.
HTH Willem


On Wed, 21 Mar 2007, Gregory Nowak wrote:

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> Hi all.
> 
> I'm trying to setup iptables, so that if I connect to localhost port
> xxx, the connection will be redirected to a machine on my internal lan
> on the same xxx port.
> 
> So, what I've put into my firewall script is:
> 
> iptables -t nat -A PREROUTING -p tcp -i lo --dport xxx -j DNAT
> - --to-destination 192.168.0.4
> 
> all on one line of course, and where xxx is a valid tcp port number.
> 
> However, when I telnet to localhost xxx, I get "trying 127.0.0.1", and
> then "connection refused", even though I am able to telnet to
> 192.168.0.4 on port xxx without a problem.
> 
> I also know for a fact that the above line works just fine if I want to expose ports from
> machines on my internal network to the outside world, using eth0
> instead of lo in those scenarios of course.
> 
> So, Can someone please tell me what I'm missing? Is it possible
> perhaps that lo cannot be treated in the same way that eth0, my
> outside interface, and eth1, my lan interface are treated? Thanks in
> advance for any help.
> 
> Greg
> 
> 
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