Networking Bible

Chapter 28. Firewalls, Gateways, and Proxy Servers

IN THIS CHAPTER

• See how firewalls can be used to protect networks

• Learn about filters you can apply

• Use Network Address Translation to keep systems hidden

• Deploy proxy servers to keep network services secure

In this chapter you learn about several different kinds of network services that are used to secure networks: firewalls, gateways, and proxy servers. These services can be implemented in software or in hardware. The use of these services helps protect a network, making it much harder for outsiders to gain unauthorized entry to private networks.

Firewalls evaluate traffic and decide which traffic to forward and which traffic to drop or return. The criteria for deciding which action to take is called a filter, and filters can be based on information in packet headers such as source address, protocol used, and many other factors. Advanced firewalls can look into packets at the Application layer performing Deep Packet Inspection. The placement of firewalls at different points in the network for different purposes is explored.

These devices perform Network Address Translation (NAT), which is explained in detail in this chapter. NAT takes a request from clients on the public network and forwards them to systems inside on a private network. This feature allows private network systems to maintain their anonymity while allowing the network to route otherwise unroutable traffic.

Gateways are systems that serve as the interface between two different ...