(The)Demilitarized zone, used to secure an internal network from external access. You can use Linux firewall to create DMZ easily. There are many different ways to design a network with a DMZ. The basic method is to use a single Linux firewall with 3 Ethernet cards. The following simple example discusses DMZ setup and forwarding public traffic to internal servers.

There's a little advanced know-how required here and he recommends a couple good firewalls to set up such functionality just in case this very useful guide doesn't fit the bill. If you are looking to set up a Linux Demilitarized zone a couple of options include EnGarde, IpCop and others.

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