CCNA 200-301 Cheat Sheet: Automation & Programmability (10%)

Quick Cues → Answers

Q: What is the fundamental difference between Ansible and Terraform?

• Ansible: Configuration management tool; agentless, push-based, YAML syntax, idempotent

• Terraform: Infrastructure as Code (IaC); declarative, manages desired state, idempotent

Q: REST API — 401 vs. 403?

• 401 Unauthorized: Authentication failed (missing/invalid credentials)

• 403 Forbidden: Authenticated but lacks permission

Q: What are the two API directions in SDN?

• Northbound API: Management → Controller (policy, intent)

• Southbound API: Controller → Devices (network state changes)

Q: Ansible agent requirement?

• None — agentless; uses SSH only

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Controller-Based Networking (SDN)

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REST APIs

|-------------|---------|-------------|

Key REST Properties

• Stateless: Each request independent; server holds no session state

• 401 Unauthorized: No valid credentials

• 403 Forbidden: Valid credentials, insufficient permissions

• 404 Not Found: Resource does not exist

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JSON Data Format

``json { "device": "router1", "interfaces": [ {"name": "Gi0/0", "ip": "10.1.1.1"}, {"name": "Gi0/1", "ip": "10.2.1.1"} ], "enabled": true, "port": 22 } ` |---------|------|---------| ---

Configuration Management Tools

|---------|-----------|--------------|

Ansible Playbook Structure

`yaml ---

• hosts: all_routers

gather_facts: no tasks: - name: Configure OSPF cisco.ios.ios_config: commands: - router ospf 1 - network 10.0.0.0 0.0.0.255 area 0 `` ---

Network Automation Impact

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AI & Machine Learning in Networking

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Easily-Confused Pairs

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Concept	Definition	Example
SDN	Separation of control plane from data plane	OpenFlow, OpenDaylight
Northbound API	Controller ← Management apps	REST API to Catalyst Center
Southbound API	Device ← Controller	OpenFlow, NETCONF, RESTCONF
Intent-Based Networking (IBN)	User defines intent; system enforces policy	Catalyst Center assurance
Catalyst Center	Cisco's SDN controller for enterprise	Replaces old Prime Infrastructure
SD-WAN	Decoupled WAN control; branch autonomy	Viptela (Cisco), Meraki
HTTP Method	Purpose	Status Code
GET	Retrieve resource	200 OK
POST	Create new resource	201 Created
PUT	Replace entire resource	200 OK / 204 No Content
PATCH	Partial update	200 OK / 204 No Content
DELETE	Remove resource	204 No Content
Element	Type	Example
String	Text, quoted	"hostname": "R1"
Number	Integer or float	"port": 22
Boolean	true/false	"enabled": true
Array	Ordered list, [ ]	[{"if": "Gi0/0"}]
Object	Key-value pairs, { }	{"name": "R1"}
null	No value	"description": null
Feature	Ansible	Terraform
Type	Config mgmt (push)	Infrastructure as Code (declarative)
Agent	None (agentless/SSH)	None required; uses APIs
Syntax	YAML (playbooks)	HCL (modules)
State	Task-based (imperative)	Desired state (declarative)
Idempotent	Yes (by design)	Yes (apply multiple times safely)
Primary Use	Device configuration, app deployment	Cloud/infrastructure provisioning
Push vs. Pull	Push (controller → devices)	Pull (state file)
Benefit	Meaning
Consistency	Same config across all devices; reduces human error
Speed	Deploy 100 devices in seconds vs. hours manual
Version Control	Git tracks all changes; audit trail and rollback capability
Scalability	Add devices without manual intervention
Intent-Based	Admin specifies "what" not "how"; controller enforces
Use Case	Application
Anomaly Detection	Catalyst Center Assurance; flagging unusual traffic patterns
Predictive Maintenance	ML models predict link failure before it occurs
Security Threat Detection	Behavioral ML for zero-day intrusion detection
Network Optimization	Auto-tuning QoS policies based on traffic history
Pair	Distinction
Northbound vs. Southbound	North = management → controller (policy); South = controller → devices (config)
401 vs. 403	401 = bad credentials; 403 = good credentials, no permission
Ansible vs. Terraform	Ansible = push config mgmt; Terraform = declarative IaC
Idempotent vs. Imperative	Idempotent = same result every run; Imperative = step-by-step instructions
Agentless vs. Agent-based	Ansible = agentless (SSH only); Puppet/Chef = agent (removed from v1.1)

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High-Yield