ZyXEL Communications Broadband Security Gateway P-312 - Manual (Page 181)

P312 Broadband Security Gateway
Creating Custom Rules 16-1
Chapter 16
Creating Custom Rules
16.1 Rules Overview
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.
If you try to configure rules but do not have a good understanding of how rules work,
you might inadvertently introduce security risks to the firewall and to the protected
network. You should be 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 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 access to a Web server to everyone but competitors.
♦
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.
16.2 Rule Logic Overview
Please note these points carefully before beginning to configure rules.
16.2.1 Rule Checklist
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?