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This article provides solutions to the error "The namespace cannot be queried. The RPC server is unavailable" that occurs when you access, modify, or create a Distributed File System (DFS) namespace.
Original KB number: 2021914
When you access, modify, or create a DFS Namespace on a DFS Namespace server, domain member server, or Windows client with File Services tools (included in Remote Server Administration Tools (RSAT)) installed, you might receive the following error message:
The namespace cannot be queried. The RPC server is unavailable.
Cause 1: The DFS Namespace service is stopped or in an undefined state
You use the DFS Management console locally and receive this error on the DFS Namespace server. It might indicate that the DFS Namespace service on the DFS Namespace server is stopped or in an undefined state but not "Running."
Resolution for cause 1: Start the DFS Namespace service
Note
After you apply the solution, remove the DFS Namespace from the DFS Management console and add it back, or close and reopen the console to make the changes take effect.
To resolve the issue, start the DFS Namespace service.
Run the following PowerShell cmdlet to check if the DFS Namespace service is running:
Get-Service -Name Dfs
If the DFS Namespace service isn't started, run the following PowerShell cmdlet to start the DFS Namespace service:
Start-Service -Name Dfs
Note
If you can't start the DFS Namespace service, it indicates a registry corruption or a service dependency issue. Ensure the dependency services of the DFS Namespace service are running properly, or import the registry settings from a backup. Then, start the DFS Namespace service again. For more information, see Resolution for cause 4: Import the registry key from a valid registry backup.
Cause 2: The DFS Namespace service is stopped or the DFS Namespace server can't be reached
If you use the DFS Management console from a domain-joined member server (not a DFSN server) or a domain client with RSAT File Services tools installed, this error might occur when:
Scenario 1
The DFS Namespace service on the DFS Namespace server is stopped or in an undefined state but not "Running."
Scenario 2
The domain-joined member server (not a DFS Namespace) or the Windows client with RSAT File Services tools installed, where you run the DFS Management console, can't reach the DFS Namespace server over TCP port 445 (used by Server Message Block (SMB)).
Wireshark trace
Scenario 1
192.168.0.45 192.168.0.42 SMB2 190 Create Request File: netdfs 192.168.0.42 192.168.0.45 SMB2 130 Create Response, Error: STATUS_OBJECT_NAME_NOT_FOUNDScenario 2
The Domain Name System (DNS) queries for A records of the DFS Namespace servers.
192.168.0.45 192.168.0.1 DNS 79 Standard query 0x429a A SRV2022.contoso.com 192.168.0.1 192.168.0.45 DNS 95 Standard query response 0x429a A SRV2022.contoso.com A 192.168.0.42However, establishing a TCP connection to the DFS Namespace server on TCP port 445 (used by SMB) fails.
192.168.0.45 192.168.0.42 TCP 66 60345 → 445 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM 192.168.0.45 192.168.0.42 TCP 66 [TCP Retransmission] 60345 → 445 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM 192.168.0.45 192.168.0.42 TCP 66 [TCP Retransmission] 60345 → 445 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM 192.168.0.45 192.168.0.42 TCP 66 [TCP Retransmission] 60345 → 445 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM 192.168.0.45 192.168.0.42 TCP 66 [TCP Retransmission] 60345 → 445 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM
Resolution for cause 2: Start the DFS Namespace service or allow TCP port 445
Note
After you apply the solution, remove the DFS Namespace from the DFS Management console and add it back, or close and reopen the console to make the changes take effect.
To resolve the issue:
Scenario 1
Start the DFS Namespace service.
Run the following PowerShell cmdlet to check if the DFS Namespace service is running:
Get-Service -Name DfsIf the DFS Namespace service isn't started, run the following PowerShell cmdlet to start the DFS Namespace service:
Start-Service -Name DfsScenario 2
Make sure that TCP port 445 (used by SMB) to the DFS Namespace server is allowed and that the server service (LanmanServer) is started.
Cause 3: No DomainDNSName records are registered for the domain
This error is typically seen in an environment using a third-party DNS server. It can occur when no DomainDNSName records are registered for the domain. These records are updated by the Netlogon service on domain controllers. These are the "same as parent" A records in the domain's forward lookup zone.
The following documentation indicates these records aren't a requirement and are only used for DNS clients that don't understand SRV records:
How DNS Support for Active Directory Works
| Host (A) resource record | Description |
|---|---|
| DnsDomainName | Enables a non-SRV-aware client to locate any domain controller in the domain by looking up an A record. A name in this form is returned to the LDAP client through an LDAP referral. A non-SRV-aware client looks up the name; an SRV-aware client looks up the appropriate SRV resource record. |
In a network trace, you'll see a DNS lookup for the DomainDNSname A record and the DNS server will respond with the SOA record if these A records don't exist.
DNS lookup query:
Dns: QueryId = 0x887C, QUERY (Standard query), Query for contoso.com of type Host Addr on class Internet
QRecord: contoso.com of type Host Addr on class Internet
Response with the SOA record:
Dns: QueryId = 0x887C, QUERY (Standard query), Response - Success
QRecord: contoso.com of type Host Addr on class Internet
AuthorityRecord: contoso.com of type SOA on class Internet: PrimaryNameServer: SRVPdc.contoso.com, AuthoritativeMailbox: hostmaster.contoso.com
Resolution for cause 3: Update the A records on the DNS server or create a HOSTS file
Note
After you apply the solution, remove the DFS Namespace from the DFS Management console and add it back, or close and reopen the console to make the changes take effect.
Update the "same as parent" A records on the third-party DNS servers.
Note
Restarting the Netlogon service on Windows domain controllers repopulates all the missing SRV records under the _msdcs.contoso.com zone. Make sure that AD replication is possible or runs successfully so that the changes about the SRV records are replicated correctly troughout your domain.
As an exceptional workaround for exceptional situations:
If the preceding solution doesn't show positive results within 30 minutes after applying, you can implement the following method as a temporary workaround. Only use this workaround until you've updated the "same as parent" A records on the third-party DNS servers.
On the computer you'll use the DFS Management console, create a HOSTS file that includes the fully qualified name and the IP addresses of the domain controllers.
Sample for the HOSTS file entry:
- contoso.com 192.168.0.1
- contoso.com 192.168.0.2
- contoso.com 192.168.0.3
Cause 4: Registry values for stand-alone DFS Namespaces are missing
One or both of the registry values ID and Svc with the REG_BINARY type under the DFS root registry path Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DFS\Roots\Standalone\<YourDfsStandaloneNamespace>, are missing.
In this case, the DFS Namespace service can crash, stop responding or even fail to start, resulting in this error.
Resolution for cause 4: Import the registry key from a valid registry backup
Note
After you apply the solution, remove the DFS Namespace from the DFS Management console and add it back, or close and reopen the console to make the changes take effect.
Important
This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For protection, back up the registry before you modify it so that you can restore it if a problem occurs. For more information about how to back up and restore the registry, see How to back up and restore the registry in Windows.
Importing the registry key for the DFS Namespace root, from a valid registry backup (if available), of the same registry key, can resolve the issue.
If no backup is present, and since you have only a single DFS root server for your namespace in a DFS stand-alone namespace configuration, the only option is to delete the DFS Namespace, perform a DFS Namespace cleanup on the DFS root server, and re-create the DFS Namespace.
Note
Restart the DFS server or the DFS server service so that the changes in the registries are loaded into memory again. Not restarting the DFS server or the DFS server service might result in the same error.