Yes, an internet connection is required because the Autodesk license server will check installations occasionally via the web. If it fails to verify the license after a certain amount of time it will start a countdown to a cutoff date as a determent to pirating the software. AutoCAD is available to download any time as a free trial that will last 30 days but once you have exhausted that timeframe you will have to look at licensing models that will allow you to continue since the free download is only intended for evaluation purposes. That being said you may use the 30 day to work on commercial projects as far as I understand, but you only get one 30 day trial so the point is to familiarize you with how it works and once you see the benefits, encourage you to become a customer.
