200-301 Question 473
Select 3An enterprise network is transitioning to a software-defined architecture using a controller-based model. The network engineer explains that the controller will manage the overlay network, while the physical devices in the network will form the underlay. Which of the following statements correctly describe the roles of overlay, underlay, and fabric in this architecture?
- A
The underlay consists of physical devices and links that provide IP connectivity between endpoints.
- B
The overlay is responsible for abstracting the physical network and enabling virtualized communication between endpoints.
- C
The fabric is a combination of the underlay and overlay, providing end-to-end communication and policy enforcement.
- D
The underlay directly enforces network policies such as Quality of Service (QoS) and security.
- E
The overlay network operates without dependency on the underlay.
Show answer and explanation
Correct answers: A, B, C
Explanation
In a controller-based, software-defined architecture, the underlay provides the physical connectivity between devices, while the overlay abstracts this layer to enable advanced features like virtualization, segmentation, and centralized management. Together, the underlay and overlay form the fabric, which delivers end-to-end communication and policy enforcement. Understanding these roles is key to implementing and managing software-defined networks.
- A. Correct.
Correct: The underlay network is the foundation of the architecture, consisting of physical devices and links that provide basic IP routing and connectivity.
- B. Correct.
Correct: The overlay network abstracts the physical network layer, creating logical tunnels or paths to deliver virtualized communication and advanced features.
- C. Correct.
Correct: The fabric integrates both the underlay and overlay to provide end-to-end connectivity, centralized management, and policy enforcement.
- D. Incorrect.
Incorrect: Policies such as QoS and security are typically managed in the overlay or fabric layer, not directly enforced by the underlay.
- E. Incorrect.
Incorrect: The overlay network relies on the underlay for physical connectivity and transport; they are interdependent.