For those that aren’t familiar with Cisco HREAP, it is a design for Wireless LANs in which only control traffic gets tunneled back to the controller and the data traffic stays local on the switch. The IEEE protocol used to communicate between an AP and a controller is called CAPWAP. There are various use cases for the technology, not described here, but that is the 100,000 foot overview.
So, looking at the diagram below, we see a very basic implementation of HREAP.