Which protocol does an SD-Access wireless Access Point use for its fabric data plane?

GRE is a generic tunneling protocol used in other overlay scenarios but is not the data plane encapsulation used by the SD-Access fabric.

MPLS is a label-switching technology used in service provider cores and is not part of the SD-Access fabric architecture.

SD-Access uses VXLAN (RFC 7348) as its overlay data plane encapsulation to carry segmented traffic between fabric nodes. A wireless AP operating as a fabric edge node encapsulates and decapsulates VXLAN frames directly, extending the fabric overlay to wireless clients. LISP serves the control plane for endpoint mapping, while VXLAN handles the actual data forwarding.

LISP (Locator/ID Separation Protocol) serves as the SD-Access control plane for mapping endpoint identifiers to routing locators; it is not the data plane encapsulation protocol.

CAPWAP is used for the wireless management plane between access points and the Wireless LAN Controller (WLC), but it is not the SD-Access fabric data plane protocol.