Microsoft Knowledge Base Article 321708 contains the following summary:
This article describes how to use the Network Diagnostics Tool (Netdiag.exe) in Windows 2000. Netdiag is a command-line diagnostic tool
that you can use to test network connectivity. It performs a series of tests to determine the state and functionality of your network client.
You can use the results of these tests and network status information that is provided by Netdiag to help you isolate network and connectivity
problems on your Windows 2000-based workstation or server computer.
Netdiag is included with the Windows 2000 Support Tools. To install the Support Tools, run Setup.exe from the Support\Tools folder on the Windows 2000 CD-ROM. To download Netdiag, visit the following Microsoft Web site:
NOTE: Before you use Netdiag to test network connectivity, Transmission Control Protocol/Internet Protocol (TCP/IP) must be bound to one or more network adapters.