Configuration Examples

NAT32 Version 2 uses a Packet Classifier to gather additional information about packets prior to routing. Its IP Router then uses this information to make complex routing decisions that allow many different network configurations to be supported. Several of those configurations are described below.

One Network, One or Two Gateways

Configuration A

The above configuration consists of a private network ( behind two external routers, each of which has its own connection to the Internet. For example, each router might use a DSL, Cable or 3G Internet connection, and each such connection will generally have different connection characteristics. The two routers are directly connected and have the IP addresses and

NAT32 can run on any (or all) of the private machines on the network.

Configuration consists of selecting the computer's network interface and then specifying that it is an Internet-connected interface. In the subsequent Interface Configuration dialog box, the two gateway addresses ( and should be entered. When NAT32 then runs, all Windows traffic will be intercepted and routed to either Gateway 1 or Gateway 2 in accordance with the selected Gateway Selection Algorithm. In addition, all DNS requests will be intercepted by NAT32's DNS Resolver to protect your users from unwanted content.

If NAT32 is to run on only a single machine, and if the other machines are to forward traffic via NAT32, then the following points should be noted:

  1. Configure the Windows TCP/IP protocol on the NAT32 machine to use a fixed IP address on the network, and then set both the default gateway address and the DNS address to
  2. Turn off the DHCP Server functionality in each external router and then enable the NAT32 DHCP Server functionality on the NAT32 Internet interface (see DHCPD for details).
  3. Reconfigure each of the other private machines either by rebooting them or running the commands ipconfig /release followed by ipconfig /renew in a Windows Console.

Two Networks, One or Two Gateways

Configuration B

The above configuration consists of a private network ( behind two external routers, and just a single machine ( on that network. The other private machines connect to a second private network ( to which the NAT32 machine connects via a second network adapter. That adapter should be configured under Windows to use a fixed IP address on the network. No gateway or DNS address need be specified. When NAT32 runs, its DHCP Server will be enabled by default, and all of the private 192.168.1.x machines will be configured correctly.

This configuration has the advantage that the private machines on the network are isolated from the Internet and protected by two external firewalls: the external router(s) and the NAT32 router. You can then safely turn off the Windows Firewall on the private machine and enjoy enhanced performance and the real protection that only external firewalls can offer.


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