Acing the CCNA Exam, Volume 2

11 Security concepts

This chapter covers

• Key security concepts and common attacks
• User authentication via passwords and alternatives
• Controlling and tracking user access with AAA
• Securing a network with firewalls and IPS

The most secure network would be a closed system, like a house with no doors or windows. But just like a house with no doors or windows would be uninhabitable, a completely isolated network would be counterproductive. The entire purpose of a network is connectivity—the ability to share, communicate, and access resources both within and outside of its confines.

In the real world, networks need to interact with other networks, applications, and users. But this interconnectivity introduces vulnerabilities from a variety of angles, ...