ZyXEL Communications P-2608HWL-Dx Series User Manual

P-2608HWL-Dx Series User’s Guide

Chapter 15 Firewalls

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

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. 

 to configure default firewall settings. 

 to configure firewall rules. 

 to configure a custom service. 

 to configure firewall thresholds. 

There are three main types of firewalls:

• Packet Filtering Firewalls
• Application-level Firewalls
• Stateful Inspection Firewalls

Packet filtering firewalls restrict access based on the source/destination computer network 
address of a packet and the type of application.