Which technology provides logical Layer 2 and Layer 3 networks in Cisco SD-Access?

The overlay network in Cisco SD-Access provides the logical Layer 2 and Layer 3 networks for user and device segmentation. It uses VXLAN (Virtual Extensible LAN) encapsulation to create these logical networks over the physical underlay. This allows for flexible placement of endpoints and consistent policy enforcement regardless of their physical location. The underlay network is the physical infrastructure (routers, switches) that provides IP reachability between network devices; it does not create logical networks. VPN Routing/Forwarding (VRF) is a technology for creating multiple routing tables within a single router, used in SD-Access within the overlay for segmentation, but it's not the overarching technology providing the logical networks. Easy Virtual Network (EVN) is a Cisco technology similar to VRF-Lite but is not the primary mechanism for logical network creation in SD-Access.