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1. Does this rule stop LAN users from accessing critical resources on the Internet? For example, if IRC is
blocked, are there users that require this service?
2. Is it possible to modify the rule to be more specific? For example, if IRC is blocked for all users, will a
rule that blocks just certain users be more effective?
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 plugging the information into
the correct fields in the web configurator screens.
11.3.3 Key Fields For Configuring Rules
Action
Should the action be to Block or Forward?
"Block" means the firewall silently discards the packet.
Service
Select the service from the Service scrolling list box. If the service is not listed, it is necessary to first define
it. See section 11.8 for more information on predefined services.
Source Address
What is the connection's source address; is it on the LAN or WAN? Is it a single IP, a range of IPs or a
subnet?
Destination Address
What is the connection's destination address; is it on the LAN or WAN? Is it a single IP, a range of IPs or a
subnet?
11.4 Connection Direction Examples
This section describes examples for firewall rules for connections going from LAN to WAN and from WAN
to LAN.
LAN to LAN/ZyWALL, WAN and WAN/ZyWALL rules apply to packets coming in on the associated
interface (LAN or WAN respectively). LAN to LAN/ZyWALL means policies for LAN-to-ZyWALL (the
Firewall Screens
ZyWALL 2 Series User's Guide
11-3
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