正解:C
Cisco SD-Access uses VXLAN as the basis for its data plane technology. VXLAN, or Virtual Extensible LAN, is a network virtualization technology that allows for the creation of a logical network on top of a physical network. It encapsulates Ethernet frames in a UDP packet, which enables the creation of overlay networks that are scalable and can span across geographically dispersed data centers. VXLAN is a crucial component of the SD-Access architecture, providing the data plane encapsulation that allows for the separation of control and data planes, which is a defining characteristic of software-defined networking (SDN).
References: Cisco SD-Access Solution Design Guide1, Cisco SD-Access Deployment Best Practices2, DNA SD-Access: Network of the Future3.