ZyXEL Communications Corporation AMG1302 Manuel D’Utilisation

Chapter 10 Firewalls

AMG1302-T10A User’s Guide

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 Device’s default rules. 

Change the default password via web configurator.

Think about access control before you connect to the network in any way.

Limit who can access your router.

Don't enable any local service (such as telnet or FTP) that you don't use. Any enabled service could 

present a potential security risk. A determined hacker might be able to find creative ways to misuse 

the enabled services to access the firewall or the network.

For local services that are enabled, protect against misuse. Protect by configuring the services to 

communicate only with specific peers, and protect by configuring rules to block packets for the 

services at specific interfaces.

Protect against IP spoofing by making sure the firewall is active.

Keep the firewall in a secured (locked) room.

Note: Incorrectly configuring the firewall may block valid access or introduce security 

risks to the Device and your protected network. Use caution when creating or 

deleting firewall rules and test your rules after you configure them.

Consider these security ramifications before creating a rule:

Does this rule stop LAN users from accessing critical resources on the Internet? For example, if IRC 

is blocked, are there users that require this service?

Is it possible to modify the rule to be more specific? For example, if IRC is blocked for all users, will 

a rule that blocks just certain users be more effective?

Does a rule that allows Internet users access to resources on the LAN create a security 

vulnerability? For example, if FTP ports (TCP 20, 21) are allowed from the Internet to the LAN, 

Internet users may be able to connect to computers with running FTP servers.

Does this rule conflict with any existing rules?