Zyxel-communications P-660HW-D Series Manual de usuario descargar pdf (Pagina 143)

P-660HW-D Series User’s Guide

Chapter 9 Firewalls 142

CHAPTER 9

Firewalls

This chapter gives some background information on firewalls and introduces the ZyXEL

device firewall.

9.1 Firewall Overview

Originally, the term firewall referred to a construction technique designed to prevent the

spread of fire from one room to another. The networking term “firewall” is a system or group

of systems that enforces an access-control policy between two networks. It may also be

defined as a mechanism used to protect a trusted network from an untrusted network. Of

course, firewalls cannot solve every security problem. A firewall is one of the mechanisms

used to establish a network security perimeter in support of a network security policy. It

should never be the only mechanism or method employed. For a firewall to guard effectively,

you must design and deploy it appropriately. This requires integrating the firewall into a broad

information-security policy. In addition, specific policies must be implemented within the

firewall itself.

Refer to Section 10.5 on page 157 to configure default firewall settings.

Refer to Section 10.6 on page 158 to view firewall rules.

Refer to Section 10.6.1 on page 160 to configure firewall rules.

Refer to Section 10.6.2 on page 163 to configure a custom service.

Refer to Section 10.10.3 on page 173 to configure firewall thresholds.

9.2 Types of Firewalls

There are three main types of firewalls:

• Packet Filtering Firewalls

• Application-level Firewalls

• Stateful Inspection Firewalls

9.2.1 Packet Filtering Firewalls

Packet filtering firewalls restrict access based on the source/destination computer network

address of a packet and the type of application.

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Zyxel-communications P-660HW-D Series Manual de usuario Pagina 143