Prepare Forest AD Error

Issue

Using the Skype for Business Server 2015 Deployment Wizard, the Prepare Forest task of Active Directory preparation fails on a new Skype for Business Server 2015 deployment with the following errors:

“Prepare Forest Active Directory settings execution failed on an unrecoverable error”.

“Command execution failed: Object reference not set to an instance of an object”.

PrepareForest-1

Investigation

Prepare Schema was successful, and the schema partition had been replicated before running the Prepare Current Forest task.

The user running the task is a member of Enterprise Admins.

Looking at the Deployment Log for the first time the task failed, the following error is logged:

Error: An error occurred: “Microsoft.Rtc.Management.ADConnect.ADOperationException” “Active Directory operation failed on “DC1v.x500.co.uk”. You cannot retry this operation: “Directory object not found 0000208D: NameErr: DSID-0310020A, problem 2001 (NO_OBJECT), data 0, best match of: ‘CN=Services,CN=Configuration,DC=x500,DC=co,DC=uk’

On the next run, the Deployment Wizard creates AD objects, universal groups, adds groups to universal groups, processes permissions, and then fails with the following errors:

Error: Object reference not set to an instance of an object. TaskFailed: Prepare Forest Active Directory settings execution failed on an unrecoverable error. 21/01/2018 14:41:44

TaskFailedResolution: Consult exception information and previous errors for more information on how to resolve this error.

Error: An error occurred: “System.ArgumentNullException” “Value cannot be null. Parameter name: instanceToDelete”

Resolution

Using the Skype for Business Server Management Shell, run the Enable-CsAdForest cmdlet with the following parameters.

Enable-CsAdForest -GroupDomain x500.co.uk -GlobalSettingsDomainController DC1v.x500.co.uk -GroupDomainController DC1v.x500.co.uk -GlobalCatalog DC1v1.x500.co.uk.

All of the above parameters are required.

  • GroupDomain: FQDN of the domain where the new universal security groups should be created.
  • GlobalSettingsDomainController: FQDN of a domain controller where global settings are stored.  If global settings are stored in the System container in Active Directory, then this parameter must point to the root domain controller.  If global settings are stored in the Configuration container, then any domain controller can be used and this parameter can be omitted.
  • GroupDomainController: FQDN of a domain controller where universal group information is stored.
  • GlobalCatalog: FQDN of a global catalog server in the domain.

Once Enable-CsAdForest has been ran successfully, run through the Skype for Business Server 2015 Deployment Wizard again, and the status of the Prepare Current Forest task will show as complete.

PrepareForest-2

All remaining Active Directory prepation tasks run without error.

PrepareForest-3

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