Which protocol does Software Defined Access (SDA) use to provide a tunnel between edge nodes in different fabrics?

Software Defined Access (SDA) uses Virtual Extensible LAN (VXLAN) to create overlay networks, providing a scalable tunneling mechanism between edge nodes in different fabrics. VXLAN encapsulates Layer 2 Ethernet frames within Layer 3 UDP packets, allowing virtual networks to span across physical network boundaries and providing greater scalability than traditional VLANs. GRE is a general-purpose tunneling protocol but is not the primary encapsulation used by SDA for fabric overlays. VLANs are limited to 4094 IDs and operate at Layer 2, lacking the scalability and Layer 3 independence required for large-scale SDA deployments. PPP is a data link layer protocol used for direct connections, not for overlay tunneling in an SDA fabric.