DFSDIAG tool introduced with Windows Server 2008 is an excellent utility for testing, documenting, and troubleshooting your DFS Namespaces environment. You just type DFSDiag.exe and...

voilà you got the list of the commands you can use. Oh yes you also have the “DFSDIAG_ERROR” message, but that’s because DFSDiag expect one of the commands that it has implemented. Ok let me try to explain the options you have:

/testdcs:
With this you can check the configuration of the domain controllers. It performs the following tests:

• Verifies that the DFS Namespace service is running on all the DCs and its Startup Type is set to Automatic.
• Check for the support of site-costed referrals for NETLOGON and SYSVOL.
• Verify the consistency of site association by hostname and IP address on each DC.

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