ZyXEL Communications 1000 Manuel D’Utilisation

 Chapter 24 Firewall

ZyWALL USG 1000 User’s Guide

the firewall rule to always be in effect. The following figure shows the results of 
this rule.

Figure 314   Blocking All LAN to WAN IRC Traffic Example 

Your firewall would have the following rules. 

• 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 LAN to WAN traffic.

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 second 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. You can also configure a LAN to WAN rule that allows IRC traffic from 
any computer through which the CEO logs into the ZyWALL with his/her user 
name. 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 DHCP).

Table 109   Blocking All LAN to WAN IRC Traffic Example 

1

Any

Any

Any

Any

IRC

Deny

2

Any

Any

Any

Any

Any

Allow