ZyXEL Communications P-6600HW-Tx v3 15

		Table of Contents
10.4.2 Port Forwarding: Services and Port Numbers ........................................................		152
10.4.3 Configuring Servers Behind Port Forwarding (Example) .......................................		152
10.5 Configuring Port Forwarding ...........................................................................................		153
10.5.1 Port Forwarding Rule Edit .....................................................................................		154
Part IV: Security ...................................................................................		157
Chapter 11
Firewalls.................................................................................................................................		159
11.1	Firewall Overview ............................................................................................................	159
11.2	Types of Firewalls ............................................................................................................	159
11.2.1 Packet Filtering Firewalls .......................................................................................		159
11.2.2 Application-level Firewalls ......................................................................................		160
11.2.3 Stateful Inspection Firewalls ...................................................................................		160
11.3	Introduction to ZyXEL’s Firewall .......................................................................................	160
11.3.1 Denial of Service Attacks .......................................................................................		161
11.4	Denial of Service ..............................................................................................................	161
11.4.1 Basics .....................................................................................................................		161
11.4.2 Types of DoS Attacks .............................................................................................		162
11.5	Stateful Inspection ............................................................................................................	164
11.5.1 Stateful Inspection Process ....................................................................................		165
11.5.2 Stateful Inspection and the ZyXEL Device .............................................................		166
11.5.3 TCP Security ..........................................................................................................		166
11.5.4 UDP/ICMP Security ................................................................................................		167
11.5.5 Upper Layer Protocols ............................................................................................		167
11.6	Guidelines for Enhancing Security with Your Firewall ......................................................	168
11.6.1 Security In General .................................................................................................		168
11.7	Packet Filtering Vs Firewall ..............................................................................................	169
11.7.1 Packet Filtering: ......................................................................................................		169
11.7.2 Firewall ...................................................................................................................		169
11.8	Triangle Route .................................................................................................................	170
11.8.1 The “Triangle Route” Problem ................................................................................		170
11.8.2 The “Triangle Route” Solutions ...............................................................................		171
Chapter 12
Firewall Configuration ..........................................................................................................		173
12.1 Access Methods ..............................................................................................................		173
12.2 Firewall Policies Overview ...............................................................................................		173
12.3 Rule Logic Overview ........................................................................................................		174
12.3.1 Rule Checklist ........................................................................................................		174
12.3.2 Security Ramifications ............................................................................................		174

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P-660HW-Tx v3 User’s Guide	15