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> Chapter 9 - Firewall > Firewall concepts

Firewall concepts

There are a number of foundational concepts that are necessary to have a grasp of before delving into the details of how the FortiGate firewall works. Some of these concepts are consistent throughout the firewall industry and some of them are specific to more advanced firewalls such as the FortiGate. Having a solid grasp of these ideas and terms can give you a better idea of what your FortiGate firewall is capable of and how it will be able to fit within your networks architecture.

This chapter describes the following firewall concepts:

  • What is a Firewall?
  • FortiGate Modes
  • How Packets are handled by FortiOS
  • Interfaces and Zones
  • IPv6
  • NAT
  • Quality of Service