Construct valid JSON-encoded files

📘CCNP Encore (350-401-ENCORE-v1.1)

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What is JSON?

JSON stands for JavaScript Object Notation.

JSON is:

• A text-based data format
• Easy for humans to read
• Easy for machines to parse
• Widely used in network automation, REST APIs, and controller-based networking

In modern Cisco networks, JSON is commonly used to:

• Exchange data with REST APIs
• Send configuration to controllers
• Receive operational data from devices
• Work with automation tools like Python scripts, Ansible, and Cisco DNA Center

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Why JSON Is Important for CCNP ENCOR

For the ENCOR exam, you must:

• Understand JSON structure
• Know JSON rules
• Be able to build valid JSON files
• Identify valid vs invalid JSON
• Understand how JSON is used in network automation

The exam does not test JavaScript, only JSON format and structure.

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Basic Structure of a JSON File

A JSON file is made of:

• Objects
• Arrays
• Key–value pairs

JSON Object

A JSON object:

• Is enclosed in curly braces { }
• Contains key–value pairs

Example:

{
  "hostname": "Router1"
}

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Key–Value Pairs

Key

• Must be a string
• Must be enclosed in double quotes

Value

Can be:

• String
• Number
• Boolean
• Object
• Array
• null

Example:

{
  "device": "Switch1",
  "version": 17.6,
  "managed": true
}

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Data Types in JSON

1. String

• Enclosed in double quotes
• Single quotes are not allowed

"interface": "GigabitEthernet0/1"

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2. Number

• No quotes
• Can be integer or decimal

"mtu": 1500

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3. Boolean

• Only true or false
• Lowercase only

"enabled": true

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4. null

• Represents no value

"description": null

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5. Object (Nested JSON)

An object inside another object:

{
  "device": {
    "hostname": "Router1",
    "ip": "192.168.1.1"
  }
}

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6. Array

• Enclosed in square brackets [ ]
• Can contain multiple values
• Values are separated by commas

Example:

{
  "vlans": [10, 20, 30]
}

Array of objects:

{
  "interfaces": [
    {
      "name": "GigabitEthernet0/0",
      "status": "up"
    },
    {
      "name": "GigabitEthernet0/1",
      "status": "down"
    }
  ]
}

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Rules for Valid JSON (VERY IMPORTANT FOR EXAM)

1. Use Double Quotes Only

✅ Correct:

"hostname": "Switch1"

❌ Incorrect:

'hostname': 'Switch1'

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2. No Trailing Commas

❌ Incorrect:

{
  "ip": "10.1.1.1",
}

✅ Correct:

{
  "ip": "10.1.1.1"
}

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3. Keys Must Be Strings

❌ Incorrect:

{ hostname: "Router1" }

✅ Correct:

{ "hostname": "Router1" }

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4. Proper Opening and Closing Brackets

Every { must have a }
Every [ must have a ]

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5. Case Sensitivity

JSON is case-sensitive:

"IP" ≠ "ip"

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Whitespace Does Not Matter

JSON ignores:

• Spaces
• Tabs
• Line breaks

These are both valid:

{"name":"Router1"}

{
  "name": "Router1"
}

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Common JSON Used in IT and Networking

Device Information

{
  "hostname": "CoreSwitch",
  "model": "C9500",
  "os": "IOS-XE",
  "version": "17.9.3"
}

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Interface Configuration

{
  "interface": "GigabitEthernet1/0/1",
  "ip_address": "192.168.10.1",
  "subnet_mask": "255.255.255.0",
  "enabled": true
}

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Controller or API Response

{
  "status": "success",
  "device_count": 25,
  "timestamp": "2025-12-19T10:30:00"
}

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JSON in REST APIs (Exam Focus)

In REST APIs:

• Requests are often sent in JSON
• Responses are usually returned in JSON

POST Request Example

{
  "username": "admin",
  "password": "cisco123"
}

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Response Example

{
  "token": "ABCD1234",
  "expires_in": 3600
}

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JSON vs XML (Quick Comparison for Exam)

Feature	JSON	XML
Format	Key–value	Tag-based
Readability	Easy	More complex
Size	Smaller	Larger
Common in APIs	Yes	Less common

ENCOR focuses more on JSON than XML.

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Valid vs Invalid JSON Examples

Valid JSON

{
  "router": "R1",
  "interfaces": ["Gig0/0", "Gig0/1"],
  "active": true
}

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Invalid JSON

{
  router: "R1",
  "interfaces": ["Gig0/0", "Gig0/1",],
  "active": True
}

Problems:

• Key not in quotes
• Trailing comma
• Boolean must be lowercase

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What You Must Remember for the Exam

Key Exam Points

✔ JSON uses key–value pairs
✔ Keys and string values use double quotes
✔ Supports objects and arrays
✔ No trailing commas
✔ Case-sensitive
✔ Commonly used in APIs and automation
✔ Widely used with Cisco controllers and tools

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Exam Tip

If the exam asks:

“Which JSON file is valid?”

Check in this order:

1. Double quotes only?
2. No trailing commas?
3. Correct brackets?
4. Lowercase true / false?
5. Proper nesting?

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Summary

JSON is a critical skill for modern network engineers.
For CCNP ENCOR:

• You don’t need to write programs
• You must recognize, read, and construct valid JSON
• Focus on syntax rules, data types, and structure

Mastering JSON makes automation, APIs, and controller-based networking much easier—and helps you pass the ENCOR exam confidently.

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