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Firewall Fundamentals

CHAPTER
5

TO SOME NETWORK ADMINISTRATORS, A FIREWALL is the key component of their infrastructure’s security. To others, a firewall is a hassle and a barrier to accomplishing essential tasks. In most cases, the negative view of firewalls stems from a basic misunderstanding of the nature of firewalls—their purpose and functions.

This chapter clearly defines the fundamentals of firewalls. These include what a firewall is, what a firewall does, how it performs these tasks, why firewalls are necessary, what the various types of firewalls are, and how filtering mechanisms work. Once you understand these fundamentals of firewalls, you will be able to look beyond the unschooled opinions, common mythology, and marketing hype surrounding the devices, and the crucial benefits of effective firewall architecture will become clear. Like any network tool, firewalls are useful in solving a variety of problems and in supporting essential network security.

Chapter 5 Topics

This chapter covers the following topics and concepts:

  • What a firewall is
  • Why firewalls are necessary on networks
  • How firewalls work
  • Types of firewalls
  • Options for individual and SOHO (small office/home office) firewalls
  • Common uses for host software firewalls, commercial software network firewalls, and hardware and appliance firewalls
  • Next-generation firewalls
  • Virtual firewalls
  • Differences between dual-homed and triple-homed firewalls
  • Difference between ingress and egress filtering
  • Types of firewall filtering
  • Selecting firewalls
  • Considerations for buying versus building a firewall

Chapter 5 Goals

When you complete this chapter, you will be able to:

  • Define firewalls
  • Explain the need for firewalls
  • Describe types of firewalls, including network router/interface firewalls, hardware/appliance firewalls, and host software firewalls
  • Compare and contrast software and hardware firewalls
  • Set up a broadband connection device firewall
  • Use Windows Defender Firewall
  • Compare and contrast dual- and triple-homed firewalls
  • Define the meaning of ingress and egress filtering
  • Explain standard filtering methods, including static packet filtering, network address translation (NAT) services, application proxy filtering, circuit proxy filtering, dynamic packet filtering, stateful inspection filtering, and content filtering
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