Firewall Rules Example; Figure 140 Blocking All Lan To Wan Irc Traffic Example; Table 67 Blocking All Lan To Wan Irc Traffic Example - ZyXEL Communications ZYWALL 35 User Manual

3 Does a rule that allows Internet users access to resources on the LAN create a security
vulnerability? For example, if FTP ports (TCP 20, 21) are allowed from the Internet to
the LAN, Internet users may be able to connect to computers with running FTP servers.
4 Does this rule conflict with any existing rules?
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 140 Blocking All LAN to WAN IRC Traffic Example

Your firewall would have the following configuration.

Table 67 Blocking All LAN to WAN IRC Traffic Example

# SOURCE
1 Any
Default Any
• 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:
ZyWALL 5/35/70 Series User's Guide
DESTINATIO
SCHEDULE
N
Any Any
Any Any
Chapter 11 Firewall
SERVICE ACTION
IRC Drop
Any Allow
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