Overlay network

An overlay network is a logical computer network that is layered on top of a physical network. The concept of overlay networking is distinct from the traditional model of OSI layered networks, and almost always assumes that the underlay network is an IP network of some kind.

Some examples of overlay networking technologies are, VXLAN, BGP VPNs, and IP-over-IP technologies, such as GRE, IPSEC tunnels, or SD-WAN.