In this chapter, we took a look at understanding some fundamental terminologies, the Cisco Common Classification Policy Language or C3PL, an overview of a ZBF and setting up and configuring the ZBF using both the Cisco Configuration Professional and the command-line interface methods. Using an existing router that supports the ZBF features would save an organization money if their budget is not big enough for a dedicated firewall appliance. 

In the next chapter, we are going to dive into IPsec, the protocol that drives VPN. We'll begin with understanding some terminology, how it works, and what actually happens in the background when a Virtual Private Network is establishing a secure tunnel across an unsecured network.