Verify that both Kerberos and NTLMv2 authentication are permitted (Hyper-V over SMB shares)


Nondisruptive operations for Hyper-V over SMB require that the CIFS server on a data SVM and the Hyper-V server permit both Kerberos and NTLMv2 authentication. You must verify settings on both the CIFS server and the Hyper-V servers that control what authentication methods are permitted.

About this task

Kerberos authentication is required when making a continuously available share connection. Part of the Remote VSS process uses NTLMv2 authentication. Therefore, connections using both authentication methods must be supported for Hyper-V over SMB configurations.

The following settings must be configured to allow both Kerberos and NTLMv2 authentication:

  • Export policies for SMB must be disabled on the storage virtual machine (SVM).

Both Kerberos and NTLMv2 authentication are always enabled on SVMs, but export policies can be used to restrict access based on authentication method.

Export policies for SMB are optional and are disabled by default. If export policies are disabled, both Kerberos and NTLMv2 authentication are allowed on a CIFS server by default.

  • The domain to which the CIFS server and Hyper-V servers belong must permit both Kerberos and NTLMv2 authentication.

Kerberos authentication is enabled by default on Active Directory domains. However, NTLMv2 authentication can be disallowed, either using Security Policy settings or Group Policies.

  1. Perform the following to verify that export policies are disabled on the SVM:

    1. Set the privilege level to advanced:

      set -privilege advanced

    2. Verify that the -is-exportpolicy-enabled CIFS server option is set to false:

      vserver cifs options show -vserver vserver_name -fields vserver,is-exportpolicy-enabled

    3. Return to the admin privilege level:

      set -privilege admin

  2. If export policies for SMB are not disabled, disable them:

    vserver cifs options modify -vserver vserver_name -is-exportpolicy-enabled false

  3. Verify that both NTLMv2 and Kerberos authentication are allowed in the domain.

    For information about determining what authentication methods are allowed in the domain, see the Microsoft TechNet Library.

  4. If the domain does not permit NTMLv2 authentication, enable NTLMv2 authentication by using one of the methods described in Microsoft documentation.


The following commands verify that export policies for SMB are disabled on SVM vs1:

cluster1::> set -privilege advanced
Warning: These advanced commands are potentially dangerous; use them
only when directed to do so by technical support personnel.
Do you wish to continue? (y or n): y

cluster1::*> vserver cifs options show -vserver vs1 -fields vserver,is-exportpolicy-enabled

vserver  is-exportpolicy-enabled
-------- -----------------------
vs1      false

cluster1::*> set -privilege admin