Exchange 2013 CU4

when applying CU9, do i need to do this: setup.exe /PrepareAD /IAcceptExchangeServerLicenseTerms or running plain setup.exe is fine?

i read somewhere that setup should be run with those switches.

Whether or not your AD Schema needs to be updated depends upon your initial Exchange 2013 version.  This will dictate if the AD Schema needs to be modified.  Check the values as noted in this post.

Source: http://blogs.technet.com/b/rmilne/archive/2015/06/16/exchange-2013-cu9-released.aspx

If you have a single domain with a single server, then running setup.exe on its own will be fine. The installer will run prep.

The only time you have to run the prep commands separately is when you have Exchange servers in multiple domains within the forest, when all domains that contain mailboxes need to be prepped before you can start installing the updates.

Simon.