When you are having configured a Hyper-V over SMB configuration, which means the virtual machines are running on Hyper-V host and are stored on a SMB file share, and you try to manage the virtual machine remotely from Hyper-V Manager or Failover Cluster Manager, you will run into access denied errors. The same error can also happen if you try live migrate the virtual machine. This error is caused because you are using the credentials from the machine which Hyper-V or Failover Cluster Manager is running on to access the file share via the Hyper-V host. This “double-hop” scenario is not by default not allowed because of security reasons. You can find more about Kerberos Authentication on TechNet.
To avoid this error you have to configure the SMB Constrained Delegation in Active Directory to allow this scenario for specific “double-hops”. In Windows Server 2012 Microsoft made setting up Kerberos constrained delegation much easier by introducing resource-based Kerberos Constrained Delegation. This it wasn’t that easy to deploy and required some step. In Windows Server 2012 R2 Microsoft introduced new Windows PowerShell cmdlets to configure SMB Constrained Delegation directly from PowerShell. These cmdlets are offered by the Active Directory PowerShell module.
On your management box or where ever you want to configure SMB Constrained Delegation you have to install the Active Directory PowerShell module. (You don’t need the module on the Hyper-V host or SMB file servers)
Now you can use the following cmdlets.
- Get-SmbDelegation –SmbServer FileServer
- Enable-SmbDelegation –SmbServer FileServer –SmbClient HyperVHost
- Disable-SmbDelegation –SmbServer FileServer [–SmbClient HyperVHost] [-Force]
For example if you are running a two node Hyper-V cluster and you use a Scale-Out File Server cluster (SOFS01) as virtual machine storage, the configuration could look like this.
Enable-SmbDelegation –SmbServer SOFS01 –SmbClient HyperV01 Enable-SmbDelegation –SmbServer SOFS01 –SmbClient HyperV02
Because these cmdlets only work with the new resource-based delegation, the Active Directory forest must be in “Windows Server 2012” functional level. A functional level of Windows Server 2012 R2 is not required.
And as I mentioned before you can also use System Center Virtual Machine Manager (VMM) to manage your storage, which uses a different approach and does not need the configuration of Kerberos Constrained Delegation.