ZyXEL Communications 320W User Manual

 

All contents copyright (c) 2005 ZyXEL Communications Corporation.   

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traffic will be blocked by P320W. To help users get rid of the problem and configuration tasks, P320W 

will create firewall policy automatically to allow incoming traffic if NAT is enabled in the P320Ws.   

 

 

 

Firewall FAQ 

 

A firewall is a system or group of systems that enforces an access-control policy between two networks. 

It may also be defined as a mechanism used to protect a trusted network from an untrusted network. The 

firewall can be thought of two mechanisms. One to block the traffic, and the other to permit traffic.   

The P320W is pre-configured to automatically detect and thwart Denial of Service (DoS) attacks such as 

Ping of Death, SYN Flood, LAND attack, IP Spoofing, etc. It also uses stateful packet inspection to 

determine if an inbound connection is allowed through the firewall to the private LAN. The P320W 

supports Network Address Translation (NAT), which translates the private local addresses to one public 

address. This adds a level of security since the clients on the private LAN are invisible to the Internet. 

Conceptually, there are three types of firewalls:   

1.  Packet Filtering Firewall   

2.  Application-level Firewall   

3.  Stateful Inspection Firewall   

Packet Filtering Firewalls generally make their decisions based on the header information in individual 

packets. These header information include the source, destination addresses and ports of the packets.   

Application-level Firewalls generally are hosts running proxy servers, which permit no traffic directly 

between networks, and which perform logging and auditing of traffic passing through them. A proxy 

server is an application gateway or circuit-level gateway that runs on top of general operating system such