The Cisco SD-Access data plane is based on VXLAN. Cisco SD-Access separates the fabric into functional planes: the underlay provides IP reachability, the control plane uses LISP to map endpoints to locations, and the data plane uses VXLAN encapsulation to carry user traffic across the routed underlay. VXLAN allows the fabric edge node to encapsulate endpoint traffic and forward it through the fabric while preserving virtual network and segmentation information. This is what enables SD-Access to provide Layer 2 and Layer 3 overlay services over a Layer 3 routed transport. OMP is the control-plane protocol for Cisco SD-WAN, not SD-Access. NHRP is associated with DMVPN tunnel resolution. LISP is essential in SD-Access, but its role is endpoint ID to routing locator mapping, not packet encapsulation in the data plane. Therefore, VXLAN is the correct protocol for the SD-Access data plane. Reference topics: SD-Access fabric, VXLAN data plane, LISP control plane, overlay encapsulation, routed underlay.

The Cisco SD-Access control-plane node provides the host tracking database and map-server function. SD- Access uses LISP-based control-plane behavior to separate endpoint identity from endpoint location. Fabric edge nodes register endpoints with the control-plane node, and the control-plane node maintains the endpoint- to-location database. When a fabric node needs to forward traffic to an endpoint, it queries the control-plane node so the destination endpoint can be resolved to the correct fabric location. In LISP terminology, this maps to the map-server and map-resolver role, while the SD-Access design discussion often refers to the endpoint database or host tracking database. The control-plane node does not enforce policy mapping by itself; policy is integrated with Cisco ISE and applied through scalable group policy in the fabric. It also does not function as a proxy ETR in this option set. Endpoint registration is initiated by the edge nodes, which detect local endpoints and inform the control plane. Therefore, host tracking database and map server are the correct functions. Reference topics: SD-Access control plane, LISP map server, host tracking database, EID-to- RLOC mapping.