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DFS Namespace troubleshooting guidance

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Distributed File System (DFS) Namespace is a Windows technology designed to provide distributed namespace access to file shares across an enterprise.

Troubleshooting checklist

Examine the SMB traffic to see if the issue is with getting the referral list from the namespace server or connecting to the referred file server. To do so, follow these steps:

First, filter the trace by the SMB traffic for the DFS Namespace IP address. Example filter: tcp.port==445.

Then, look for the DFS referral. Follow these steps:

  1. The protocol is named DFSC by packet capture parsers. Look for the DFSC traffic in the filtered results or append the filter with DFSC in netmon or MA: tcp.port==445 and DFSC.

  2. The client should send a DFS referral request to the DFS Namespace server. If no DFS referral is being sent, and there's no indication of a firewall or anti-virus block, restart the DFS client to clear any DFS referral caching. Then, start the data collection steps over again.

  3. The server should send a DFS referral response to the DFS client.

  4. The referral step has completed successfully if a referral list has been returned. Skip to step 4 if the referral process completed successfully.

  5. Verify whether the DFS Referral Request arrived at the DFS Namespace server. Standard TCP/IP and firewall troubleshooting applies if the referral doesn't arrive. The most likely cause is the traffic being dropped or blocked somewhere.

    If the referral request arrives but no response is sent:

    1. Make sure the Windows Firewall or another network security application isn't blocking the request.
    2. Verify Active Directory works correctly to troubleshoot the DFS Namespace server.

Look for the DFS client to resolve DNS (assuming it isn't cached) and make a connection to a file server.

  1. It's possible that Windows won't attempt to contact a referral if there are other networking issues, such as a DNS resolution failure.
  2. To ensure that Windows will perform DNS resolution, you can flush the DNS cache after starting the trace and before reproducing the issue. This operation allows you to verify that DNS resolution is working correctly.
    1. In Windows 8 and later versions of Windows, use PowerShell cmdlet: Clear-DnsClientCache.
    2. For previous versions of Windows, run command: ipconfig flushdns.

SMB troubleshooting applies to fixing the file server connection.

Common issues and solutions

Data collection

Before contacting Microsoft support, you can gather information about your issue.

Prerequisites

  1. TSS must be run by accounts with administrator privileges on the local system, and EULA must be accepted (once EULA is accepted, TSS won't prompt again).
  2. We recommend the local machine RemoteSigned PowerShell execution policy.

Note

If the current PowerShell execution policy doesn't allow running TSS, take the following actions:

  • Set the RemoteSigned execution policy for the process level by running the cmdlet PS C:\> Set-ExecutionPolicy -scope Process -ExecutionPolicy RemoteSigned.
  • To verify if the change takes effect, run the cmdlet PS C:\> Get-ExecutionPolicy -List.
  • Because the process level permissions only apply to the current PowerShell session, once the given PowerShell window in which TSS runs is closed, the assigned permission for the process level will also go back to the previously configured state.

Gather key information before contacting Microsoft support

  1. Download TSS on all nodes and unzip it in the C:\tss folder.

  2. Open the C:\tss folder from an elevated PowerShell command prompt.

  3. Start the traces on the client and the server by using the following cmdlets:

    • Client:

      TSS.ps1 -Scenario NET_DFScli

    • Server:

      TSS.ps1 -Scenario NET_DFSsrv

  4. Accept the EULA if the traces are run for the first time on the server or the client.

  5. Allow recording (PSR or video).

  6. Reproduce the issue before entering Y.

    Note

    If you collect logs on both the client and the server, wait for this message on both nodes before reproducing the issue.

  7. Enter Y to finish the log collection after the issue is reproduced.

The traces will be stored in a zip file in the C:\MS_DATA folder, which can be uploaded to the workspace for analysis.

Reference

Frequently Asked Questions