You can install multiple network adapters in a Windows 2000 / XP Professional system.

To enable Windows 2000 in such a case (System#2 in the graphic below) to enable
System #1 and System#3 to communicate with each other, System #2 has to handle
the Routing of the network traffic, it has to act as a "Router" :

What are the possibilities for System #2 using Windows9x, NT4 and Windows 2000 ?

Windows95/98/ME is able to work as a router using a registry entry( NOT supported by Microsoft ) :

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP : "EnableRouting", value "1"

Windows NT4 Workstation and Server fully support IP routing: it is activated in the Network configuration, tab: "Protocols" ,then display the properties of the TCP/IP-protocol, tab "Routing" : place a checkmark on "Enable IP Forwarding"

All documentation on Windows 2000 shows that routing on multiple network adapters is
activated in "RRAS" : Routing and Remote Access Service.
But RRAS is not part of Windows 2000 Professional.

Searching the Microsoft Website , I found:

TCP/IP Troubleshooting Troubleshooting IP Routing

Enabling IP Routing

By default, IP routing is disabled. To enable IP routing, you must allow the computer to
forward IP packets it receives. This requires a change to the Windows 2000 system registry.
When you enable the Routing and Remote Access service for IP routing,
this registry entry is made automatically.

To enable IP routing

1 .From the Start menu, click Run.

2.Type regedt32.exe or regedit.exe, and then click OK.

3.In a registry editor, navigate to
HKEY_LOCAL_MACHINE \SYSTEM\CurrentControlSet\Services\Tcpip \Parameters

4. Select the "IPEnableRouter" entry (by defining as value : 1 ) :

5. To enable IP routing for all network connections installed and used by this computer, assign a value of 1.
To do this in regedit.exe, right-click the entry, and then click Modify.
In regedt32.exe, click on the wanted entry, click on Edit, and then click on the appropriate menu choice.

6.Close the registry editor.

It is required to reboot Windows 2000 for this change to take effect.

I have used this in a configuration, where the Windows 2000 Professional system works
as a router between an Ethernet network and a USB-network.

I have found in Windows XP Professional Online Help or the Resource kit no information
on the use of Windows XP as a router, so I can only assume that Microsoft likes to reserve
this functionality for the (still to come) server-version of XP.
But since (except for the new fancy and colorful userinterface) Windows XP is very similar
to Windows 2000, I tried the same registry entry as for Windows 2000 :

HKEY_LOCAL_MACHINE \SYSTEM\CurrentControlSet\Services\Tcpip \Parameters
subkey : "IPEnableRouter" entry , was by default set to "0" "


After rebooting the system, my Windows XP system was working properly as a router between 2 different
subnets.