14

Firewalls

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

14.1 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 15.5 on page 248 to configure default firewall settings. Refer to Section 15.6 on page 249 to view firewall rules.

Refer to Section 15.6.1 on page 251 to configure firewall rules. Refer to Section 15.6.2 on page 254 to configure a custom service. Refer to Section 15.8.3 on page 260 to configure firewall thresholds.

14.2 Types of Firewalls

There are three main types of firewalls:

•Packet Filtering Firewalls

•Application-level Firewalls

•Stateful Inspection Firewalls

14.2.1Packet 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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P-2602HWLNI User’s Guide