ENCOR 06 - Automation¶

Programmability, data formats, APIs, and configuration management. Roughly 15% of the exam, and the section most likely to be unfamiliar to traditional network engineers.

Data formats¶

• JSON - key-value pairs and arrays. Objects use {}, arrays []. Values are strings, numbers, booleans, null, objects, or arrays. The dominant format in REST APIs.
• XML - tag-based and hierarchical, with opening and closing tags. Used by NETCONF.
• YAML - indentation-based, human-readable. Used by Ansible playbooks. Lists use -, mappings use key: value. Tabs are not permitted, only spaces, which is the classic YAML error.

Be able to read a snippet and identify the format and the value at a given path. Questions frequently show JSON and ask what a nested key evaluates to.

APIs¶

• REST - stateless HTTP operations on resources.
• GET retrieve, POST create, PUT replace, PATCH partially update, DELETE remove.
• Status codes: 200 OK, 201 Created, 204 No Content, 400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found, 429 Too Many Requests, 500 Server Error.
• Idempotency - GET, PUT, and DELETE are idempotent; POST is not. See idempotency explained.
• Authentication - API keys, tokens, and OAuth. Many Cisco APIs issue a time-limited token from an initial authentication call.
• Rate limiting - 429 responses mean back off; well-behaved clients implement retry with backoff.
• Webhook - a server-initiated HTTP callback, the push counterpart to polling.

Learn the verb-to-operation mapping and the common status codes. Both are directly tested.

Network programmability protocols¶

• NETCONF - XML over SSH on port 830. Operates on datastores (running, candidate, startup) with operations get, get-config, edit-config, copy-config, delete-config, lock, unlock, and commit. Supports transactions, so a failed change can be rolled back atomically.
• RESTCONF - REST over HTTPS exposing YANG models, using JSON or XML. Simpler than NETCONF but without full transaction semantics.
• YANG - the modeling language defining the structure of configuration and operational data. Models are native (vendor-specific), OpenConfig, or IETF.
• gNMI - gRPC-based, used mainly for streaming telemetry subscriptions.

NETCONF supports candidate configuration and commit, which RESTCONF does not. That difference is the usual discriminator in comparison questions.

Configuration management tools¶

• Ansible components - inventory (hosts), playbook (YAML tasks), module (the unit of work), role (reusable structure), and variables.
• Idempotency in configuration management - running the same playbook twice produces the same end state, with no change reported the second time. This is the defining property.
• Agentless advantage - nothing to install on network devices, which is why Ansible dominates network automation.

Ansible is agentless and push-based; Puppet and Chef use agents and pull. Terraform provisions infrastructure rather than configuring existing devices.

Python for network automation¶

Expect to read short scripts rather than write them.

• Common libraries - requests for REST, netmiko for SSH-based CLI automation, napalm for multi-vendor abstraction, ncclient for NETCONF, pyats/genie for testing and parsing.
• Reading JSON - response.json() produces a dictionary; index it with keys and list positions.
• Basic constructs - variables, lists, dictionaries, for loops, if statements, and function definitions.

A typical exam snippet retrieves JSON from a REST call and asks which line extracts a particular value.

Cisco platforms and on-box automation¶

• Cisco DNA Center / Catalyst Center APIs - intent-based northbound REST APIs for policy, provisioning, and assurance.
• Cisco SD-WAN vManage API - REST for the SD-WAN fabric.
• Meraki Dashboard API - REST for cloud-managed devices.
• EEM (Embedded Event Manager) - on-box automation reacting to events with applets or Tcl scripts. The answer for "act automatically on the device when X happens" without an external controller.
• Guest Shell - a Linux container on the device for running Python locally.
• Zero-touch provisioning (ZTP) - devices fetch configuration on first boot via DHCP and a script.
• Cisco Plug and Play (PnP) - Cisco's ZTP implementation within Catalyst Center.

EEM is on-box and event-driven; a controller API is off-box and centralized. Choose by whether the reaction must be local and immediate.

Intent-based networking¶

• Intent-based networking (IBN) - express the desired outcome, and the system translates it into device configuration, then continuously verifies it.
• Assurance loop - translation, activation, and assurance. The verification step is what distinguishes IBN from plain automation.

Exam pointers¶

• YAML uses spaces, never tabs.
• REST verbs: GET read, POST create, PUT replace, PATCH modify, DELETE remove.
• 401 is unauthenticated, 403 is authenticated but forbidden, 429 is rate limited.
• NETCONF is XML over SSH 830 with candidate/commit; RESTCONF is HTTP with JSON or XML.
• Ansible is agentless and push; Puppet and Chef are agent-based and pull.
• EEM performs on-box event-driven automation.
• Idempotency means re-running produces no further change.

Official documentation¶

📖 ENCOR 350-401 exam topics - authoritative blueprint 📖 Cisco DevNet - APIs, sandboxes, and learning labs 📖 NETCONF and RESTCONF programmability guide - protocol reference