(
De
Militarized 
Zone)  A middle ground between an organization's trusted internal network and an untrusted, external network such as the Internet.  Also called a "perimeter network," the DMZ is a subnetwork (subnet) that may sit between firewalls or off one leg of a firewall.  Organizations typically place their Web, mail and authentication servers in the DMZ.  DMZ is a military term that refers to the area between two enemies.  See 
bastion host, 
firewall and 
opening a port.
The DMZ
All servers exposed to the Internet (the bastion hosts) are located in the DMZ, which is isolated from the public Internet and the private LAN by screening routers.