Which of the following statements are true about the underlay and overlay concepts on a...

In Huawei's data center network architecture, an underlay network refers to the physical infrastructure comprising switches, routers, and other network equipment (e.g., VAS devices), responsible for basic IP connectivity. This supports statement B.

The overlay network is logically built on top of the underlay and uses tunneling protocols such as VXLAN (MAC-in-UDP) to encapsulate Layer 2/Layer 3 service traffic. This encapsulation ensures transparent delivery of packets across IP underlays. This supports both C and D.

Statement A is incorrect: even when using an overlay, the underlay still requires routing protocols (like OSPF, BGP) or static routes to ensure IP reachability between VXLAN Tunnel Endpoints (VTEPs). Overlay tunnels ride on top of this IP connectivity.