Quick Reference Guide

Chapter 4: Firewall Protection and Content Filtering | 43
ProSafe Dual WAN Gigabit Firewall with SSL & IPsec VPN FVS336Gv2 Reference Manual
A firewall incorporates the functions of a NAT (Network Address Translation) router, while
adding features for dealing with a hacker intrusion or attack, and for controlling the types of
traffic that can flow between the two networks. Unlike simple Internet sharing NAT routers, a
firewall uses a process called stateful packet inspection to protect your network from attacks
and intrusions. NAT performs a very limited stateful inspection in that it considers whether the
incoming packet is in response to an outgoing request, but true Stateful Packet Inspection
goes far beyond NAT.
Using Rules to Block or Allow Specific Kinds of Traffic
This section includes the following topics:
• “About Services-Based Rules” on page 43.
• “Viewing the Rules” on page 48.
• “Order of Precedence for Rules” on page 48.
• “Setting the Default Outbound Policy” on page 48.
• “Creating a LAN WAN Outbound Services Rule” on page 49.
• “Creating a LAN WAN Inbound Services Rule” on page 49.
• “Modifying Rules” on page 50.
• “Inbound Rules Examples” on page 51.
• “Outbound Rules Example” on page 53.
Firewall rules are used to block or allow specific traffic passing through from one side to the
other. Inbound rules (WAN to LAN) restrict access by outsiders to private resources,
selectively allowing only specific outside users to access specific resources. Outbound rules
(LAN to WAN) determine what outside resources local users can have access to.
A firewall has two default rules, one for inbound traffic and one for outbound traffic. The
default rules of the VPN firewall are:
• Inbound. Block all access from outside except responses to requests from the LAN side.
• Outbound. Allow all access from the LAN side to the outside.
User-defined firewall rules for blocking or allowing traffic on the VPN firewall can be applied
to inbound or outbound traffic.
About Services-Based Rules
The rules to block traffic are based on the traffic’s category of service.
• Outbound Rules (service blocking). Outbound traffic is normally allowed unless the
VPN firewall is configured to disallow it.
• Inbound Rules (port forwarding). Inbound traffic is normally blocked by the VPN
firewall unless the traffic is in response to a request from the LAN side. The VPN firewall
can be configured to allow this otherwise blocked traffic.