Autodesk is legally obligated to support activation for perpetual licenses. However, you must use the phone activation option. The online server may reject it, but the automated phone line (accessible via the activation window) will generate a code.
Before diving into specific codes, you must understand that these are two distinct pieces of data. Many users fail to activate AutoCAD 2015 because they confuse the two. autocad 2015 serial number product key
If you are a student or educator, you should be looking for a cracked serial number. Autodesk offers full access to AutoCAD 2015 (and all older versions) for free via the Educational Community. Autodesk is legally obligated to support activation for