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A Red Hat training course is available for Red Hat Enterprise Linux DMZs and IPTables

You can create iptables rules to route traffic to certain machines, such as a dedicated HTTP or FTP server, in a demilitarized zone (DMZ). A DMZ is a special local subnetwork dedicated to providing services on a public carrier, such as the Internet.
For example, to set a rule for routing incoming HTTP requests to a dedicated HTTP server at (outside of the range of the LAN), NAT uses the PREROUTING table to forward the packets to the appropriate destination:
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j DNAT --to-destination
With this command, all HTTP connections to port 80 from outside of the LAN are routed to the HTTP server on a network separate from the rest of the internal network. This form of network segmentation can prove safer than allowing HTTP connections to a machine on the network.
If the HTTP server is configured to accept secure connections, then port 443 must be forwarded as well.