Automation and Programmability

What this domain actually tests

The domain everyone under-studies, because it is newer and feels less "networky" than OSPF and VLANs.

It is 10% of the exam — roughly ten questions — and it is some of the easiest material on the paper. Two solid evenings covers it properly. Skipping it is a self-inflicted wound, and it is enough to fail you on its own if you are borderline elsewhere.

What you actually need

REST APIs and HTTP verbs. Know what each does:

Verb	Action
GET	Retrieve
POST	Create
PUT	Replace/update
PATCH	Partially update
DELETE	Remove

And the response codes: 200 OK, 201 created, 400 bad request, 401 unauthorised, 403 forbidden, 404 not found, 500 server error.

JSON structure. You will be shown a JSON blob and asked a question about it. You need to read it — objects in {}, arrays in [], key–value pairs — and identify a value or spot a syntax error. That is genuinely the level. Know how JSON differs from XML and YAML at a glance.

Controller-based (software-defined) networking. The key idea: traditional networking configures each device individually; SDN separates the control plane from the data plane and centralises the control plane in a controller. The controller pushes policy down through a southbound interface to the devices, and exposes a northbound API (usually REST) to applications and automation tools.

Northbound = toward the applications. Southbound = toward the devices. That pair is examinable.

Configuration management tools, at recognition level only:

Tool	Key trait
Ansible	Agentless, push model, uses SSH, YAML playbooks
Puppet	Agent-based, pull model
Chef	Agent-based, Ruby
Terraform	Provisioning infrastructure (not configuring existing devices)

Ansible is agentless is the single most-tested fact in that table.

The traps

"Agentless" belongs to Ansible. If a question asks which tool requires no software installed on managed devices, that is Ansible.

Configuration management is not provisioning. Ansible, Puppet, and Chef configure things that exist. Terraform creates infrastructure. The exam keeps them distinct.

Do not confuse the controller with a router. The controller does not forward traffic; it makes decisions and distributes them.

How to study it

Two evenings, deliberately scheduled — not a weekend skim after everything else.

Evening one: HTTP verbs, response codes, and reading JSON. Practise by looking at real JSON and answering questions about it.

Evening two: SDN's control-plane/data-plane split, northbound versus southbound, and the tool table.

Ten questions for two evenings of work is the best exchange rate on the entire CCNA. Take it.