📘CCNA 200-301 v1.1

6.7 Recognize components of JSON-encoded data

JSON Overview

• JSON stands for JavaScript Object Notation.
• It is a lightweight data format used to store and exchange data between devices, applications, and networks.
• In networking, JSON is commonly used in:
  • APIs (like REST APIs)
  • Network automation tools (like Ansible, Python scripts)
  • Controller-based systems (like SDN controllers)

Think of it as a standard way to structure data so devices and software can understand it.

---

JSON Components

JSON data is made up of basic components:

1. Objects

• Represent a collection of key-value pairs.
• Written inside curly braces {}.
• Key is like the name of the data, and value is the data itself.
• Example (network device info):

{
  "hostname": "Switch1",
  "ip_address": "192.168.1.10",
  "status": "active"
}

Here:

• hostname = key, "Switch1" = value
• ip_address = key, "192.168.1.10" = value
• status = key, "active" = value

---

2. Arrays

• Represent lists of items, written inside square brackets [].
• Can contain objects, strings, numbers, or even other arrays.
• Example (list of interfaces on a device):

{
  "interfaces": ["Gig0/1", "Gig0/2", "Gig0/3"]
}

Here:

• interfaces is the key
• The value is an array of three strings representing interface names.

---

3. Values

• Can be different types:
  1. String – Text enclosed in double quotes. Example: "active"
  2. Number – Numeric values. Example: 100 or 3.14
  3. Boolean – True or False. Example: true or false
  4. Null – Empty or no value. Example: null
  5. Object – Another collection of key-value pairs {}
  6. Array – A list of values []

Example combining values:

{
  "hostname": "Router1",
  "interfaces": ["Gig0/0", "Gig0/1"],
  "vlan_count": 5,
  "enabled": true,
  "description": null
}

---

4. Key Rules

• Keys must be strings in double quotes.
• Each key must be unique within an object.
• Key-value pairs are separated by a colon :.
• Multiple pairs are separated by commas ,.

Example of multiple key-value pairs:

{
  "hostname": "Switch2",
  "ip_address": "10.0.0.1",
  "status": "inactive"
}

---

5. Nested Objects

• JSON objects can be inside other objects to represent structured data.
• Example in networking: device with interfaces and VLANs

{
  "device": "Switch1",
  "interfaces": {
    "Gig0/1": {"status": "up", "vlan": 10},
    "Gig0/2": {"status": "down", "vlan": 20}
  }
}

Here:

• interfaces is an object inside the main object
• Each interface has its own status and VLAN as key-value pairs

---

Why JSON is Important in Networking

• Automation: Scripts can read/write JSON to configure devices.
• APIs: Devices send data in JSON for monitoring or management.
• Controllers: SDN controllers exchange device states in JSON.
• Consistency: Everyone (humans and machines) can understand the same format.

---

✅ Key points to remember for CCNA 200-301 exam:

1. JSON is lightweight, text-based, and used to exchange data.
2. Objects = {}, Arrays = [].
3. Values can be string, number, boolean, null, object, or array.
4. Keys must be strings in double quotes, separated from values by :.
5. JSON can be nested for complex data structures.

---