"Cannot query namespace" appears when trying to create a DFS namespace. The "RPC server is unavailable" error may be caused by the following reasons, the following is the appropriate solution:

The DFS namespace service is not started or is in an undefined state

Workaround: Check and start the DFS namespace service.

Open PowerShell and run the following command to check the DFS service status:

powershell

GetService Name Dfs

If the service is not started, run the following command to start the service:

powershell

StartService Name Dfs

If the service fails to start, there may be a registry corruption or a problem with a service dependency. Make sure all dependent services are running properly, or restore registry Settings from a backup.

The DFS namespace server cannot be accessed

Workaround: Check the network connection of the DFS namespace server.

Ensure that the server has access to the DFS namespace service.

If the server is behind a firewall, make sure the firewall allows communication over TCP port 445.

DNS configuration problem

Solution: Check the DNS configuration.

Ensure that the correct A records are registered on the DNS server for the DFS namespace server.

If you have problems with the DNS configuration, you can try creating a HOSTS file entry locally that points to the IP address of the DFS namespace server.

The registry key is missing or damaged

Workaround: Import registry keys from a valid registry backup.

If there is a backup, restore the registry key in the root directory of the DFS namespace from the registry backup.

If there is no backup, you may need to delete the DFS namespace, perform a DFS namespace cleanup, and recreate the DFS namespace.

Domain controller problem

Solution: Check the network connection of the domain controller.

Ensure that the primary domain controller (PDC) or domain controller (DC) is accessible.

Check whether TCP/UDP port 389 (LDAP) is working properly.

The LDAP SRV record is missing. Procedure

Workaround: Ensure that all necessary LDAP SRV records exist in DNS.

Check the DNS server to ensure that the correct LDAP SRV records are configured for the domain controller.

Restart the DFS service or server

Workaround: Restart the DFS service or the entire server.

Restart the DFS service to reload changes in the registry.

If the problem persists, restart the DFS server to ensure that all configurations take effect.

If the problem persists, you are advised to further check the configuration of the DFS namespace or refer to Microsoft's official documentation.