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.
