ZyXEL p-660h-61 Betriebsanweisung

Prestige 660H Series User’s Guide 

Creating Custom Rules 

         12-1 

Firewall rules are subdivided into “Local Network” and “Internet”. By default, the Prestige’s stateful 
packet inspection allows all communications to the Internet that originate from the local network, and 
blocks all traffic to the LAN that originates from the Internet. You may define additional rules and sets 
or modify existing ones but please exercise extreme caution in doing so. 

You might inadvertently introduce security risks to the firewall and to the protected network, if you try 
to configure rules without a good understanding of how rules work. 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 network traffic’s Source IP address, Destination IP address, IP 
protocol type to rules set by the administrator. Your customized rules take precedence, and may 
override the Prestige’s default rules.  

Study these points carefully before configuring rules. 

1.  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.” 

2.  Is the intent of the rule to forward or block traffic? 

3.  What is the direction connection: from the LAN to the Internet, or from the Internet to the LAN? 

4.  What IP services will be affected? 

5.  What computers on the LAN are to be affected (if any)? 

6.  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.