This chapter showed you the basics of firewalls and design considerations in firewall systems. You were introduced to different generations of firewalls and their functions, and you learned how to design a good firewall system. This can be something as simple as setting up a basic packet filtering firewall, to something as complex as using a stateful firewall with DMZs, ALG authenticated user connections, authenticating user connections, using different scanning techniques to probe host behind firewalls, and making use of many other features.
In the next chapter, we will discuss VPNs in a public internet infrastructure, as well as different attributes within an IPsec framework.
