Network Address Translation (NAT) Server:

Nat us an Internet Protocol (IP) translation process that allows a network with private addresses to access information on the Internet. If the NAT routing protocol is installed and configured on a server that runs Routing and Remote Access, internal network clients with private Internet Protocol (IP) addresses can access the Internet through the external interface of the NAT server. This is much like of a proxy server but it does not have any cache.

To configure server 2003 as a NAT server

Follow these steps to accomplish the task

1.         On the Administrative Tools menu, click Routing and Remote Access.

2.         In the Routing and Remote Access, expand your server_name (where server_name is the name of the server that you want to configure) and then expand IP Routing in the left pane.

3.         Right-click General and then click New Routing Protocol.

4.         Click to select the NAT/Basic Firewall check box and then click OK.

5.         Right-click NAT/Basic Firewall in the left pane and then click New Interface.

6.         Click the interface that represents your internal network interface and then click OK.

7.         In the Network Address Translation properties, click Private interface connected to private network and then click OK.

8.         Right-click NAT/Basic Firewall in the left pane and then click New Interface.

9.         Click the interface that represents your external network interface and then click OK.

 

10.      In Network Address Translation properties, click Public interface connected to the Internet. For a dial-up connection to the Internet, select the demand-dial interface that is configured to connect to your ISP. Click to select the Enable NAT on this interface check box and then click OK.

 

The NAT server can automatically assign IP addresses to internal network clients. You may want to use this functionality if you do not have a DHCP server that is already assigning addressing information to clients on the internal network.

To Configure NAT Server to Assign IP Addresses and Perform Proxy DNS Queries

Follow these steps in order to accomplish the task

1.         Right-click NAT/Basic Firewall in the left pane and then click Properties.

2.         Click the Address Assignment tab and then click to select the Automatically assign IP addresses by using the DHCP allocator check box.

3.         In the IP address box, type a network ID.

4.         In the Mask box, type a subnet mask.

5.         You can also exclude IP addresses from the range you are defining so that the excluded IP addresses can be assigned to specific computers on the private network by clicking Exclude and adding IP addresses.

6.         Click the Name Resolution tab and then click to select the Clients using Domain Name System (DNS) check box.

7.         If you use a demand-dial interface to connect to the Internet, click to select the Connect to the public network when a name needs to be resolved check box.

8.         In the Demand-dial interface box, click the interface to dial.

9.         Click Apply and then click OK.

To Configure a Windows Server 2003-Based Computer to Use a NAT Server

Follow these steps in order to accomplish the task

1.       Open Network Connections, right click Local Area Connection and click Properties.

 

2.       Click Internet Protocol (TCP/IP) and Click Properties.

3.       In the Default gateway box, type the internal IP address of the NAT server and your IP address with Mask.

4.       Click OK, click OK, and then click Close.

If your computer receives its IP address from a Dynamic Host Configuration Protocol (DHCP) server, click Advanced, click the IP Settings tab, under Gateway click Add, type the internal IP address of your NAT server, click Add, click OK.

Summary:

After you follow these basic configuration steps, internal network clients can access servers on the Internet. When internal network clients send a request for the Internet, the NAT protocol driver intercepts the request and forwards the request to the destination Internet server. All requests appear to come from the external IP address of the NAT server. This process hides your internal IP addresses scheme.  The NAT server can also perform Domain Name System (DNS) queries on the behalf of NAT clients. The Routing and Remote Access NAT server resolves the Internet host name that is included in the client request and then forwards the IP address to the client. If you are using

an interface other than a network adapter (for example, a dial-up networking connection) to connect to the internet that does not appear in the New Interface Properties then you have to make a Demand Dial Interface for that connection. To make a Demand Dial Interface see our article”How to Make a Demand Dial Interface in RRAS in Windows Server 2003”.