iptables help please

[Gregory Nowak <greg@romuald.net.eu.org>]

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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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