ZyXEL P-2602HW Benutzerhandbuch

Chapter 15 Firewall Configuration

P-2602H(W)(L)-DxA User’s Guide

You may define additional rules and sets or modify existing ones but please exercise 
extreme caution in doing so.

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If you configure firewall rules without a good understanding of how they work, 
you might inadvertently introduce security risks to the firewall and to the 
protected network. Make sure you test your rules after you configure them.

For example, you may create rules to:

• Block certain types of traffic, such as IRC (Internet Relay Chat), from the LAN to the 

Internet.

• Allow certain types of traffic, such as Lotus Notes database synchronization, from specific 

hosts on the Internet to specific hosts on the LAN.

• Allow everyone except your competitors to access a Web server.
• Restrict use of certain protocols, such as Telnet, to authorized users on the LAN.

These custom rules work by comparing the Source IP address, Destination IP address and IP 
protocol type of network traffic to rules set by the administrator. Your customized rules take 
precedence and override the ZyXEL Device’s default rules. 

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Study these points carefully before configuring rules.

State the intent of the rule. For example, “This restricts all IRC access from the LAN to the 
Internet.” Or, “This allows a remote Lotus Notes server to synchronize over the Internet to an 
inside Notes server.”

1 Is the intent of the rule to forward or block traffic?
2 What direction of traffic does the rule apply to?
3 What IP services will be affected?
4 What computers on the LAN are to be affected (if any)?
5 What computers on the Internet will be affected? The more specific, the better. For 

example, if traffic is being allowed from the Internet to the LAN, it is better to allow 
only certain machines on the Internet to access the LAN.

1 Once the logic of the rule has been defined, it is critical to consider the security 

ramifications created by the rule: