Chapter 19 Firewall

19.5 Firewall Rule Example Applications

Suppose you decide to block 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 172 Blocking All LAN to WAN IRC Traffic Example

Your firewall would have the following rules.

Table 102 Blocking All LAN to WAN IRC Traffic Example

#

USERSOURCE

DESTINATION

SCHEDULESERVICEACTION

1

Any

Any

Any

Any

IRC

Deny

 

 

 

 

 

 

 

2

Any

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 LAN1 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 you need to let the CEO use IRC. You configure a LAN1 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 DHCP Settings on page 173 for information on DHCP).

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