ZyXEL Communications G.SHDSL.bis 4-port Security Gateway P-793H - Manual (Page 133)

P-793H User’s Guide
Chapter 9 Firewall Configuration 133
4 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.
5 Does this rule conflict with any existing rules?
6 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.
9.3.3 Key Fields For Configuring Rules
9.3.3.1 Action
Should the action be to Drop, Reject or Permit?
Note: “Drop” means the firewall silently discards the packet. “Reject” means the
firewall discards packets and sends an ICMP destination-unreachable
message to the sender.
9.3.3.2 Service
Select the service from the Service scrolling list box. If the service is not listed, it is necessary
to first define it. See
Appendix E on page 389 for more information on predefined services.
9.3.3.3 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?
9.3.3.4 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?
9.4 Connection Direction
This section describes examples for firewall rules for connections going from LAN to WAN
and from WAN to LAN.
LAN to LAN/ Router and WAN to WAN/ Router rules apply to packets coming in on the
associated interface (LAN or WAN, respectively). LAN to LAN/ Router means policies for
LAN-to-ZyXEL Device (the policies for managing the ZyXEL Device 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/ Router polices apply in the same way to the WAN
port.