Which API in an SDN architecture is used by applications to interact with the controller?
Correct Answer: C
Detailed Explanation: In SDN, northbound APIs provide the interface between the SDN controller and higher-level applications or orchestration systems. They enable applications to query the network, push policies, and receive network status information without needing to know the low-level details of the underlying infrastructure. The northbound API (Option C) is essential for integrating business logic with network operations. Southbound APIs, like OpenFlow, work in the opposite direction, communicating between the controller and the network devices. Options B and D are not standard API terms in SDN.
This CCNA practice question helps students prepare for Cisco networking certification exams by testing knowledge of network fundamentals, routing, switching, and network security concepts.