You can upgrade to Cloud Foundation 2.1.1 only if you are at Cloud Foundation 2.1. If your environment includes a Cloud Foundation version prior to 2.1, you must first upgrade to 2.1 and then upgrade to 2.1.1.
Ensure that the General Prerequisites Before Upgrading are met before you begin the upgrade.
Upgrading Cloud Foundation is a multi step process. You must follow each step in the order in which it is documented.