ZyXEL Communications 2 Plus User Manual

Chapter 11 Firewall

ZyWALL 2 Plus User’s Guide

Once these questions have been answered, adding rules is simply a matter of entering the 
information into the correct fields in the web configurator screens.

Suppose that your company decides to block all of the LAN users from using IRC (Internet 
Relay Chat) through the Internet. To do this, you would configure a LAN to WAN firewall 
rule that blocks IRC traffic from any source IP address from going to any destination address. 
You do not need to specify a schedule since you need the firewall rule to always be in effect. 
The following figure shows the results of this rule.

Figure 132   Blocking All LAN to WAN IRC Traffic Example 

Your firewall would have the following configuration.  

• The first row blocks LAN access to the IRC service on the WAN. 
• The second row is the firewall’s default policy that allows all traffic from the LAN to go to 

the WAN.

The ZyWALL applies the firewall rules in order. So for this example, when the ZyWALL 
receives traffic from the LAN, it checks it against the first rule. If the traffic matches (if it is 
IRC traffic) the firewall takes the action in the rule (drop) and stops checking the firewall 
rules. Any traffic that does not match the first firewall rule will match the default rule and the 
ZyWALL forwards it.  
Now suppose that your company wants to let the CEO use IRC. You can configure a LAN to 
WAN firewall rule that allows IRC traffic from the IP address of the CEO’s computer. In order 
to make sure that the CEO’s computer always uses the same IP address, make sure it either:

• has a static IP address, 
• or you configure a static DHCP entry for it so the ZyWALL always assigns it the same IP 

address (see 

 for information on static DHCP).  

Table 46   Blocking All LAN to WAN IRC Traffic Example 

1

Any

Any

Any

IRC

Drop

Default

Any

Any

Any

Any

Allow