802.11g ADSL 2+ 4-Port Security Gateway User Guide

P-662H/HW-D Series User’s Guide
Table of Contents 15
9.3 NAT General Setup .........................................................................................160
9.4 Port Forwarding ................................................................................................161
9.4.1 Default Server IP Address ......................................................................162
9.4.2 Port Forwarding: Services and Port Numbers ........................................162
9.4.3 Configuring Servers Behind Port Forwarding (Example) ........................163
9.5 Configuring Port Forwarding ...........................................................................163
9.5.1 Port Forwarding Rule Edit .......................................................................164
9.6 Address Mapping ............................................................................................165
9.6.1 Address Mapping Rule Edit ....................................................................167
Chapter 10
Firewalls................................................................................................................ 169
10.1 Firewall Overview ..........................................................................................169
10.2 Types of Firewalls ..........................................................................................169
10.2.1 Packet Filtering Firewalls ......................................................................169
10.2.2 Application-level Firewalls ....................................................................170
10.2.3 Stateful Inspection Firewalls ................................................................170
10.3 Introduction to ZyXEL’s Firewall .....................................................................170
10.3.1 Denial of Service Attacks ......................................................................171
10.4 Denial of Service ............................................................................................171
10.4.1 Basics ...................................................................................................171
10.4.2 Types of DoS Attacks ...........................................................................172
10.4.2.1 ICMP Vulnerability ......................................................................174
10.4.2.2 Illegal Commands (NetBIOS and SMTP) ....................................174
10.4.2.3 Traceroute ...................................................................................175
10.5 Stateful Inspection ..........................................................................................175
10.5.1 Stateful Inspection Process ..................................................................176
10.5.2 Stateful Inspection and the ZyXEL Device ............................................176
10.5.3 TCP Security .........................................................................................177
10.5.4 UDP/ICMP Security ..............................................................................177
10.5.5 Upper Layer Protocols ..........................................................................178
10.6 Guidelines for Enhancing Security with Your Firewall ....................................178
10.6.1 Security In General ...............................................................................179
10.7 Packet Filtering Vs Firewall ............................................................................179
10.7.1 Packet Filtering: ....................................................................................180
10.7.1.1 When To Use Filtering .................................................................180
10.7.2 Firewall .................................................................................................180
10.7.2.1 When To Use The Firewall ..........................................................180
Chapter 11
Firewall Configuration ......................................................................................... 181
11.1 Access Methods .............................................................................................181
11.2 Firewall Policies Overview ..............................................................................181