Which API is used in controller-based architectures to interact with edge devices?

A.

In controller-based architectures, network devices such as switches, routers, and access points are managed centrally by a network controller. This controller interacts with the network devices using a specific set of APIs.

The APIs used in controller-based architectures to interact with edge devices are called "southbound APIs". These APIs allow the controller to communicate with the network devices and configure them based on policies defined by the network administrator.

Southbound APIs are typically proprietary and specific to each vendor's implementation. For example, Cisco uses its own southbound APIs in its controller-based architectures, such as the Cisco Application Centric Infrastructure (ACI) and Cisco Software-Defined Access (SD-Access) solutions.

In contrast, "northbound APIs" are used to allow external applications to interact with the controller and access network services. These APIs provide a standardized interface for applications to communicate with the controller and use its services.

Overlay and underlay refer to network architecture concepts. The overlay network refers to the logical network built on top of the physical network, while the underlay network refers to the physical network infrastructure that supports the overlay network.

Therefore, the correct answer to the question is A. southbound.