Simple Secure Network Design

Simple Secure Network Design

In Chapter 1, you saw a simplified example of a secure network design. Figure 5-1 expands on that view. The perimeter router represents the border crossing or the demarcation point between the outside world and the internal network.

Figure 5-1: Network design with perimeter security

In a small branch office or in a telecommuter’s home, a single perimeter router might be the only barrier between the inside and outside network. The features and configuration of that lone device would be the only line of defense. Many larger networks use a design similar to that shown in Figure 5-1, called screened subnet architecture. In screened subnet architecture, two devices work together with a router as the perimeter device and the firewall as the second line of defense. The result is three types of networks: inside, outside, and an area called the demilitarized zone (DMZ).