Can't prepare an Active Directory forest in Skype for Business Server 2015 Content provided by Microsoft Applies to: Skype for Business Server 2015 Select Product Version All ProductsSkype for Business Server 2015 Symptoms When you run forest preparation to prepare an Active Directory forest in a Microsoft Skype for Business Server 2015 environment, the preparation process fails. Cause This issue occurs because the values of the rangeUpper and rangeLower attributes are incorrect in the "CN=ms-RTC-SIP-ServiceSchemaVersion,CN=Schema,CN=Configuration,DC=..." container. Resolution To fix this issue, install the March 2016 cumulative update 6.0.9319.235 for Skype for Business Server 2015, core components. Last Updated: Jan 7, 2017 Was this information helpful? Yes No Tell us what we can do to improve the article Submit Thanks! Your feedback will help us improve the support experience.