I can't locate the option to enable IP forwarding on my Windows 2000 Professional system. To enable this option under Windows NT 4.0, I simply selected the Enable IP Forwarding check box in the Control Panel Network applet's TCP/IP Properties dialog box. Can you direct me to the Win2K equivalent of this setting?
As you describe, enabling IP forwarding (i.e., routing) in NT 4.0 is a simple matter. Enabling the option in Win2K is another story. IP forwarding is disabled by default on all Win2K systems, and you can't use the GUI to enable the option. Instead, you must make the change in the registry.
On your Win2K Pro system, open regedit and navigate to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters subkey. Set the value for the IPEnableRouter entry (of type REG_DWORD) to 1, or add the entry if it doesn't exist. This change enables IP forwarding for all network connections on the computer. (For information about this registry change, see the Microsoft article "How to Enable TCP/IP Forwarding in Windows 2000" at http://support.microsoft.com/support/kb/articles/q230/0/82.asp.)
Note that IP forwarding is most useful on Win2K Pro systems that you use as routers and isn't usually necessary or recommended for Win2K servers running RRAS, Microsoft Internet Security and Acceleration (ISA) Server 2000, Microsoft Proxy Server, or other routing or Internet proxy or gateway applications. Such applications can inherently manage IP traffic between network interfaces and don't require—or might be adversely affected by—this registry modification.