Re: [LARTC] PAT HOW to - IPTABLES

[Grant Taylor <gtaylor@riverviewtech.net>]

On 12/10/07 04:20, Indunil Jayasooriya wrote:
> @ DMZ ZONE I have 3 web servers. But I have only one real ip on my 
> firewall. Now , I want to forward port 80 to theese 3 web servers.
> 
> How can I do it?

Like someone else suggested, run a reverse proxy on one system.  You 
could either run it on the firewall or a fourth system in the DMZ so 
that you are not running it on the firewall.  Use this reverse proxy to 
intelligently redirect queries that come in to it to the correct back 
end server.

In short, you are forwarding HTTP traffic to an application layer 
gateway that is intelligent enough to pick the proper back end system to 
handle the requests.  For SMTP, you would use something like Sendmail 
with Mailertable.

With regards to others comments about the single IP and not being able 
to communicate with the internal servers, you can use private IP 
addresses in your DMZ with out a problem so long as they are all hidden 
from the world by your NATing router such that everyone would think that 
all your services are coming off of your one single external IP.  You 
will need to pay attention to SMTP Hello names as well.

Also be aware that you are having a lot depend on connection tracking on 
the NATing router, thus have a finite number of resources that are being 
shared by multiple systems.  If it is still in place you may want to 
consider running stateless nat (IPRoute2) for your traffic coming in to 
said systems so that that traffic will not exceed conntrack.



Grant. . . .
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