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Networking Fundamentals · Foundational

Demilitarized Zone (DMZ)

A network segment between an organization's internal network and the Internet that hosts public-facing services.

Definition

The DMZ isolates servers such as web, mail and DNS so a compromise does not directly expose the internal network. Firewall rules allow limited traffic from the Internet to the DMZ and tightly restrict traffic from the DMZ inward. CompTIA now uses the term screened subnet.

Example

A public web server sits in the DMZ behind the perimeter firewall.

Exam tip

Screened subnet = DMZ on current CompTIA exams. SOHO routers' "DMZ host" feature simply forwards all ports to one host.

Related terms