AN Lesson-15

Configuring NAT

NAT Concepts

Network Address Translation (NAT)

•   NAT is a service built into a router that modifies the header information in IP datagrams before sending them on to their destinations.
• The computer on which NAT is configured can act as a network address translator, a simplified DHCP server, a DNS proxy, and a Windows Internet Name Service (WINS) proxy. Figure 9-27 illustrates this service.

NAT Configuration

You can configure NAT through a demand-dial interface or through a persistent connection. A demand-dial interface connects only when a client requests the connection. A persistent connection can be either a dedicated line such as a DSL or T1 line or a dial-up interface that automatically redials when the line is dropped.

Internet Connection Sharing	Network Address Translation
Single check box configuration	Manual configuration
Single public IP address	Single or multiple public IP addresses
Fixed address range (192.168.0.0/24) for internal hosts	Configurable address range for internal hosts
Single internal interface connecting to a                          single logical subnet	Single or multiple internal interfaces connecting to a single logical subnet
Installed using Network And Dial-Up Connections	Installed using Routing And Remote Access Console
Microsoft Windows 98 Second  Edition or later	Windows 2000 Server or Windows Server 2003
Windows Firewall	Basic Firewall

Troubleshooting NAT

1. NAT requires that the appropriate external (public) and internal (private) interfaces be added to the NAT protocol in the Routing And Remote Access console.

2. NAT requires that a default static route be added in the Routing And Remote Access console.

3. NAT requires that a DHCP service be properly configured for internal clients.

4. For NAT to be used in conjunction with DNS name resolution, a DNS server must either be configured on the NAT computer or specified through the DNS proxy in NAT.

5. Certain NAT features require more complex configuration.

1. What is Network Address Translation? Describe the difference between ICS and NAT?

2. How to Troubleshoot NAT? Discuss at least five Troubleshooting points.