APIs and REST Fundamentals

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Lesson 134Interactive lesson

APIs and REST Fundamentals

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Lesson format19 sections3 code blocks1 practice itemUpdated Oct 2, 2026

bash

curl -X GET https://sandboxdnac.cisco.com/dna/system/api/v1/auth/token -H "Authorization: Basic $(echo -n 'devnetuser:Cisco123!' | base64)" -k

That single command authenticates to Cisco's public DNA Center sandbox and requests an API token. Real production controllers work the same way — you authenticate, get a token, and use that token for subsequent requests. Every modern controller and many network devices expose a REST API.

#What Is a REST API#link

▪Representational State Transfer — an architectural style, not a protocol
▪Uses HTTP as the transport (the same HTTP that serves web pages)
▪Stateless — each request carries all needed information
▪Resource-oriented — URLs identify resources (devices, interfaces, VLANs)
▪Uses standard HTTP methods (GET, POST, PUT, DELETE, PATCH)
▪Typically returns JSON (sometimes XML)

#HTTP Methods#link

Method	Purpose	Example
GET	Retrieve a resource	Get device list
POST	Create a new resource	Create a new VLAN
PUT	Replace an existing resource	Update full device config
PATCH	Modify part of a resource	Change device description
DELETE	Remove a resource	Delete a VLAN

callout

PUT and PATCH are subtle. PUT replaces the entire resource — if you PUT a partial object, you may wipe out fields you didn't include. PATCH modifies only what you send. For network automation, always prefer PATCH when available — a PUT with a partial object can silently erase configuration.

#The REST Request/Response Flow#link

#Authentication#link

Authenticate and get a token

root@vulnarex:~#TOKEN=$(curl -s -X POST https://sandboxdnac.cisco.com/dna/system/api/v1/auth/token -H 'Authorization: Basic ZGV2bmV0dXNlcjpDaXNjbzEyMyE=' | jq -r '.Token')

root@vulnarex:~#echo $TOKEN

The base64-encoded string after `Basic` is `devnetuser:Cisco123!`. That's the username:password in base64 — HTTP Basic authentication. The controller verifies the credentials and returns a JSON Web Token (JWT). The token goes in the `Authorization: Bearer <token>` header of subsequent requests.

#Making an API Call#link

bash

# Using the token to get a list of devices
curl -X GET https://sandboxdnac.cisco.com/dna/intent/api/v1/network-device \
  -H "X-Auth-Token: $TOKEN" \
  -H "Content-Type: application/json" \
  -k | jq '.response[0]'

# Expected output (abbreviated):
# {
#   "id": "a1b2c3d4-...",
#   "hostname": "sw1.example.com",
#   "managementIpAddress": "10.10.20.10",
#   "platformId": "C9300-48P",
#   "softwareVersion": "17.9.4a",
#   ...
# }

That's a GET request with the token in the `X-Auth-Token` header (DNA Center's convention — some APIs use `Authorization: Bearer`). The response is JSON — parsed here with `jq` for readability. In Python, you'd use the `requests` library instead of curl.

#Check Your Understanding#link

★ 15 XPeasy

SYNTAX VALIDATION (★ 15 XP)

Which HTTP method is used to retrieve a resource? (single word)

root@vulnarex:~#

Press Enter to submit

Authenticate to the DNA Center sandbox (sandboxdnac.cisco.com, user devnetuser, password Cisco123!). Retrieve the token. Then call the network-device endpoint and list the first three devices. Verify your token is being accepted by checking the HTTP status code (should be 200).

callout

REST APIs are how you programmatically interact with controllers and modern devices. Authenticate, get a token, make requests with the token. Learn the HTTP methods and their semantics. Section 18 continues with JSON and hands-on Python automation.

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What Is a REST API HTTP Methods The REST Request/Response Flow Authentication Making an API Call Check Your Understanding

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October 2, 2026

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curl -H "Accept: text/markdown" "https://vulnarex.com/api/content/lessons?courseSlug=complete-ccna-200-301&lessonSlug=3-apis-rest-fundamentals&lang=en&format=markdown"

MCP Server Config (mcp.json)

{
  "mcpServers": {
    "vulnarex": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-fetch"],
      "env": { "MCP_FETCH_URL": "https://vulnarex.com" }
    }
  }
}

MCP Server Card/.well-known/mcp.json A2A Agent Card/.well-known/agent-card.json API Catalog/.well-known/api-catalog robots.txt/robots.txt

Laboratory sanity code

Isolate active probes on matched virtual networks and keep execution streams sandboxed.

Method

Purpose

Example

GET

Retrieve a resource

Get device list

POST

Create a new resource

Create a new VLAN

PUT

Replace an existing resource

Update full device config

PATCH

Modify part of a resource

Change device description

DELETE

Remove a resource

Delete a VLAN

# Using the token to get a list of devices

curl -X GET https://sandboxdnac.cisco.com/dna/intent/api/v1/network-device \

-H "X-Auth-Token: $TOKEN" \

-H "Content-Type: application/json" \

-k | jq '.response[0]'

# Expected output (abbreviated):

# {

# "id": "a1b2c3d4-...",

# "hostname": "sw1.example.com",

# "managementIpAddress": "10.10.20.10",

# "platformId": "C9300-48P",

# "softwareVersion": "17.9.4a",

# ...

# }