Which of the following components are typically part of a controller‑based, software‑defined networking (SDN) architecture? (Select all that apply.)
Correct Answer: A,B,C,E
Detailed Explanation: In a controller‑based SDN architecture, the network is divided into distinct layers that together form a flexible, programmable network. The underlay network (Option A) consists of the physical infrastructure (routers, switches, cables) that provides the basic connectivity. On top of this lies the overlay network (Option B), which is a virtualized layer that abstracts the physical details and enables the creation of virtual networks. This separation allows administrators to design and manage virtual network segments independent of the underlying hardware. A network fabric (Option C) is often used to describe an integrated, converged network environment that seamlessly combines the physical underlay with the logical overlay, ensuring efficient, high‑performance connectivity across the network. Central to the SDN architecture is the SDN controller (Option E), which centralizes the control plane. The controller manages network behavior and enforces policies through southbound APIs (to devices) and northbound APIs (to applications). This centralized approach contrasts with traditional networks, where the control plane is distributed (Option D, which is incorrect here, as SDN intentionally removes the distributed control plane). The separation and abstraction provided by the overlay and underlay networks, combined with centralized control via the SDN controller, allow for greater network flexibility, easier management, and rapid adaptation to changing conditions.
This CCNA practice question helps students prepare for Cisco networking certification exams by testing knowledge of network fundamentals, routing, switching, and network security concepts.