loaded on them. The first mode is called standalone (or
NX-OS) mode, which means the switches act like regular
Layer 2/Layer 3 data center devices that are usually
managed individually. In the second mode, ACI mode,
the Cisco Nexus devices are part of an ACI fabric and are
managed in a centralized fashion. The central controller
for the ACI fabric is the Cisco Application Policy
Infrastructure Controller (APIC). This controller is the
main architectural component of the Cisco ACI solution
and provides a single point of automation and
management for the Cisco ACI fabric, policy
enforcement, and health monitoring. The Cisco APIC
was built on an API-first architecture from its inception.
On top of this API, a command-line interface (CLI) and a
graphical user interface (GUI) have been developed. The
API is exposed through a REST interface and is
accessible as a northbound interface for users and
developers to integrate and develop their own custom
solutions on top of the Cisco APIC and Cisco ACI fabric.
The Cisco APIC interacts with and manages the Cisco
Nexus switches through the OpFlex protocol, which is
exposed as a southbound interface. From an SDN
controller perspective (similar to the Cisco DNA Center
controller described in Chapter 8, “Cisco Enterprise
Networking Management Platforms and APIs”), a
northbound interface specifies the collection of protocols
that a user can use to interact with and program the
controller, while a southbound interface specifies the
protocols and interfaces that the controller uses to
interact with the devices it manages. Some of the
features and capabilities of the Cisco APIC are as follows:
Application-centric network policy for physical, virtual, and cloud
infrastructure
Data model–based declarative provisioning
Designed around open standards and open APIs
Cisco ACI fabric inventory and configuration
Software image management
Fault, event, and performance monitoring and management