Hello. I have an exchange on-premises 2013 server environment like this: -Active Directory 1EA -Client Access 1EA (exchange 2013 cu8) -Mailbox Database 2EA (exchange 2013 cu8) The exchange version is 2013 CU 8. I am planning an upgrade to CU 23. During the upgrade process, There is setup.exe /prepareAD command execution. On which server should I execute this command? Case 1. When upgrading cu23 on a 3 EA server with cu 8 installed, execute it 3 times, one each. Case 2. Among the 3EA servers with cu 8 installed, after executing the setup.exe /prepareAD command only in 1EA, upgrade cu 23 without executing it on the rest of the servers. Case 3. Execute setup.exe /prepareAD only in Active Directory server. Which of the above 3 cases should I choose? Additional questions) Exchange 2013 When upgrading from cu 8 to cu 23, setup.exe /prepareschema Should I run this command too? As far as I know, the schema version is the same, so I don't think you need to run it, right?