User manual

Chapter 24 Firewall

ZyWALL USG 300 User’s Guide

453

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

this rule.

Figure 338 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,

• You configure a static DHCP entry for it so the ZyWALL always assigns it the

same IP address (see DHCP Settings on page 360 for information on DHCP).

Table 117 Blocking All LAN to WAN IRC Traffic Example

# USER SOURCE DESTINATION SCHEDULE SERVICE ACTION

1 Any Any Any Any IRC Deny

2 Any Any Any Any Any Allow