CCNA® Cisco Certified Network Associate: Study Guide, Seventh Edition

Perimeter, Firewall, and Internal Routers

You see this a lot—typically, in medium to large enterprise networks, the various strategies for security are based on some recipe of internal and perimeter routers plus firewall devices. Internal routers provide additional security by screening traffic to various parts of the protected corporate network, and they do this using access lists. You can see where each of these types of devices are found in Figure 12-1.

I’ll use the terms trusted network and untrusted network throughout this chapter and in Chapter 13, “Network Address Translation (NAT),” so it’s important that you can see where they are found in a typical secured network. The demilitarized zone (DMZ) can be global (real) Internet addresses ...