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ZyWALL 50 Internet Security Gateway
Table Of Contents xi
6.2.1 SUA (Single User Account) Versus NAT ..........................................................................6-6
6.2.2 Applying NAT ....................................................................................................................6-6
6.3 NAT Setup..................................................................................................................................6-8
6.3.1 Address Mapping Sets ........................................................................................................6-8
6.4 NAT Server Sets – Port Forwarding.........................................................................................6-13
6.4.1 Configuring a Server behind NAT....................................................................................6-14
6.5 General NAT Examples............................................................................................................6-16
6.5.1 Internet Access Only.........................................................................................................6-16
6.5.2 Example 2: Internet Access with an Inside Server............................................................6-17
6.5.3 Example 3: Multiple Public IP Addresses With Inside Servers........................................6-18
6.5.4 Example 4: NAT Unfriendly Application Programs.........................................................6-22
FIREWALL AND CONTENT FILTERS.....................................................................................................III
Chapter 7 Firewalls..................................................................................................................................7-1
7.1 What Is a Firewall?.....................................................................................................................7-1
7.2 Types of Firewalls ......................................................................................................................7-1
7.2.1 Packet Filtering Firewalls ...................................................................................................7-1
7.2.2 Application-level Firewalls.................................................................................................7-1
7.2.3 Stateful Inspection Firewalls...............................................................................................7-2
7.3 Introduction to ZyXEL’s Firewall ..............................................................................................7-2
7.4 Denial of Service ........................................................................................................................7-3
7.4.1 Basics..................................................................................................................................7-3
7.4.2 Types of DoS Attacks .........................................................................................................7-4
7.5 Stateful Inspection ......................................................................................................................7-7
7.5.1 Stateful Inspection Process .................................................................................................7-8
7.5.2 Stateful Inspection and the ZyWALL.................................................................................7-9
7.5.3 TCP Security.....................................................................................................................7-10
7.5.4 UDP/ICMP Security .........................................................................................................7-10
7.5.5 Upper Layer Protocols......................................................................................................7-11