Once you create an iSCSI target on Windows Server 2012 there doesn’t seem to be a way to add/ remove initiator IDs via the GUI. But you can use PowerShell for it.
Set-IscsiServerTarget is your friend.
PS> Set-IscsiServerTarget TargetName LUN -InitiatorIds Iqn:iqn.1991-05.com.microsoft:win-data01.rakhesh.local,Iqn:iqn.1991-05.com.microsoft:win-data02.rakhesh.local
Bear in mind this replaces the existing list with the new one.
A cool thing about most of these iSCSI cmdlets is that they work remotely too. So one can add a
-ComputerName xxx switch to work with a remote computer.