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| Part II |

# Part II: Building Firewalls

Part II describes how to build firewalls, configure services to run with them, and maintain firewalls over time.

Chapter 4, Firewall Design, outlines the basic components and major architectures used in constructing firewalls -- dual-homed hosts, screened hosts, screened subnets, and variations on these basic architectures.

Chapter 5, Bastion Hosts, presents step-by-step instructions for how to design and build the bastion hosts used in many firewall configurations.

Chapter 6, Packet Filtering, describes how proxy clients and servers work, and how to use these systems in building a firewall.

Chapter 7, Proxy Systems, describes how packet filtering systems work and discusses what you can and can't accomplish with them in building a firewall.

Chapter 8, Configuring Internet Services, describes how to configure each major Internet service to run with a firewall.

Chapter 9, Two Sample Firewalls, presents two sample configurations for basic firewalls.

Chapter 10, Authentication and Inbound Services, discusses the problem of allowing users to access your systems from the Internet, and describes a variety of authentication strategies and products.

3.8 Simplicity |  | 4. Firewall Design