What Is an API?
An API (Application Programming Interface) is a defined way for one program to ask another for data or actions — a contract for software-to-software communication. In networking, APIs let you configure and query devices with code instead of typing CLI commands by hand.
The restaurant analogy
Think of an API as a waiter. You (a program) don't walk into the kitchen (another system) — you give the waiter a structured order (a request), and they bring back exactly what you asked for (a response). The menu is the API's documentation: the list of what you're allowed to ask for and how.
REST APIs — the web standard
Most modern network APIs are REST APIs over HTTPS. You send an HTTP request to a URL (an endpoint) with a method — GET to read, POST to create, PUT to update, DELETE to remove — and get back structured data, usually in JSON. See REST APIs for networking.
GET /api/devices/router1/interfaces → { "interfaces": [ ... ] }Why APIs matter in networking
APIs are how automation happens. Instead of logging into 200 switches by hand, a script calls each device's API (or a controller like DNA Center) to push config or pull status in seconds. This is why the CCNA now includes APIs — see Python for network engineers and Ansible.
Frequently asked questions
What is an API in simple terms?
An API is a defined way for one piece of software to request data or actions from another — like a waiter taking your order to the kitchen and bringing back exactly what you asked for.
What is a REST API?
A REST API is a web API that uses HTTP methods (GET, POST, PUT, DELETE) against URL endpoints and typically returns JSON. It is the most common style of network device and controller API.
Why do network engineers need to know APIs?
Because network automation works through APIs — scripts and tools configure and query devices via APIs instead of manual CLI, letting you manage hundreds of devices at once. APIs are now part of the CCNA.
What data format do APIs use?
Most modern APIs return JSON; some use XML or YAML. JSON is the most common because it is lightweight and easy for both programs and people to read.
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