Model FVL328 ProSafe High-Speed VPN Firewall Reference Manual
5-12
Protecting Your Network
M-10144-01
Understanding the Order of Precedence for Rules
As you define new rules, they are added to the tables in the Rules menu, as shown below.
Figure 5-7: Rules table with examples
For any traffic attempting to pass through the firewall, the packet information is subjected to the
rules in the order shown in the Rules Table, beginning at the top and proceeding to the default rules
at the bottom. In some cases, the order of precedence of two or more rules may be important in
determining the disposition of a packet. The Move button allows you to relocate a defined rule to a
new position in the table.
Regulating Access to Network Services
Services are functions performed by server computers at the request of client computers. For
example, Web servers serve Web pages, time servers serve time and date information, and game
hosts serve data about other players’ moves. When a computer on the Internet sends a request for
service to a server computer, the requested service is identified by a service or port number. This
number appears as the destination port number in the transmitted IP packets. For example, a packet
that is sent with destination port number 80 is an HTTP (Web server) request.
