Tech Note: Configuring Windows as a router
Configuring Windows NT 4.0 as a routerI am using a PC running Windows NT 4.0 Workstation, Service Pack 3, as a router to connect several machines to the Internet over a single modem. To do this, your Internet access provider must give you a block of IP addresses that you can assign to the machines on your network. Microsoft publishes a comprehensive tech note describing the requirements and configuration: Article ID: Q121877 Using RAS for Routing of IP packets
Note: that documentation has one step that's not clear, be sure the registry key DisableOtherSrcPackets is set to 0 Registry: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\RasArp\ Parameters Add Value name: DisableOtherSrcPackets Data Type: REG_DWORD Data: 0
You should check out a diagram of my network configuration, which consists of three PCs.
Configuring Windows NT 3.51 as a routerUsing Windows NT, you can connect an entire LAN to the Internet over the same modem. I got things running pretty easily once I cobbled together the following instructions. These describe how I configured my system when I was running NT 3.51, service pack 5. Before you begin, you should be relatively comfortable with Windows NT system management and TCP/IP concepts.
1) get your access provider to route a block of addresses to you
HKEY_LOCAL_MACHINE \System\CurrentControlSet\Services\RasArp\Parameters\DisableOtherSrcPackets Data type REG_DWORD, value = 0 HKEY_LOCAL_MACHINE \System\CurrentControlSet\Services\Tcpip\Parameters\IPEnableRouter Data type REG_DWORD, value = 15) On other machines on your LAN, set gateway to the IP of the machine used as the router.
6) NOTE: if you have a recent NT Service Pack installed, you must have the IP addresses of your LAN on a different subnet than your incoming RAS connection. For instance, let's say your service provider routes packets to address xxx.xxx.xxx.1 (your incoming RAS connection on the router PC). Configure the ethernet card on that PC to be xxx.xxx.xxx.129 and use a Subnet Mask of 255.255.255.128. Give the other PCs on your LAN IP addresses above 129 and the same subnet mask.
You are all set. When the router machine is online, dialed into your access provider, it will route IP packets to and from any other machine on your network. In fact, you can configure additional modems on the router as RAS dial-in ports...you are then an Internet access provider in your own right!
Last update: December 21, 1997