In Huawei CloudFabric architecture, the underlay network is the physical IP fabric, while the overlay network is a logical network built on top of it using technologies like VXLAN and BGP EVPN .

Option A is false because the overlay network does not require bare optical fibers . It operates independently of the physical medium and can run over any IP-based underlay (Ethernet, optical, etc.). The overlay abstracts the physical infrastructure.

Option B is correct : the underlay network is transparent to endpoints (servers, firewalls, routers). These devices only interact with the overlay and are unaware of the underlying transport.

Option C is correct : the overlay has its own forwarding plane (VXLAN encapsulation) and control plane (BGP EVPN) , enabling scalable and automated network virtualization.

Option D is correct : the overlay is a logical network built over the underlay , providing tenant isolation and flexible service deployment.

Huawei best practices emphasize decoupling overlay from underlay , ensuring flexibility, scalability, and simplified operations.

Therefore, the correct answer is A .