Chapter 11 Firewall

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.

11.5 Firewall Rules Example

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.

Table 46 Blocking All LAN to WAN IRC Traffic Example

#

SOURCE

DESTINATIO

SCHEDULE

SERVICE

ACTION

N

 

 

 

 

 

1

Any

Any

Any

IRC

Drop

 

 

 

 

 

 

Default

Any

Any

Any

Any

Allow

 

 

 

 

 

 

•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 Section 6.8 on page 139 for information on static DHCP).

200

 

ZyWALL 2 Plus User’s Guide