Connection Direction Examples - ZyXEL Communications ZyWALL 5 User Manual

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.
10.3.3 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 10.8 for more information on predefined services.
Source Address
What is the connection's source address; is it on the LAN, DMZ 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, DMZ or WAN? Is it a single IP, a
range of IPs or a subnet?

10.4 Connection Direction Examples

This section describes examples for firewall rules for connections going from LAN to WAN and from
WAN to LAN. Rules for the DMZ work in a similar fashion.
LAN to LAN/ZyWALL, WAN to WAN/ZyWALL and DMZ to DMZ/ZyWALL rules apply to
packets coming in on the associated interface (LAN, WAN, or DMZ respectively). LAN to
LAN/ZyWALL means policies for LAN-to-ZyWALL (the policies for managing the ZyWALL
through the LAN interface) and policies for LAN-to-LAN (the policies that control routing between
two subnets on the LAN). Similarly, WAN to WAN/ZyWALL and DMZ to DMZ/ZyWALL polices
apply in the same way to the WAN and DMZ ports.
10.4.1 LAN to WAN Rules
The default rule for LAN to WAN traffic is that all users on the LAN are allowed non-restricted access
to the WAN. When you configure a LAN to WAN rule, you in essence want to limit some or all users
from accessing certain services on the WAN. See the following figure.
Firewall Screens
ZyWALL 5 Internet Security Appliance
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