Understanding REST APIs in Networking: A Beginner’s Guide

In networking, managing devices and monitoring networks can be complex. REST APIs, which stands for Representational State Transfer Application Programming Interfaces, provide a way for network devices and management tools to communicate with each other over the network. Instead of manually configuring devices through a console or GUI, REST APIs allow automated access to information and actions, making network management faster and more efficient.

In this blog, we’ll explain REST APIs from a networking perspective. You’ll learn how they work, the common methods used, and why they are becoming an essential tool for modern network automation and monitoring.

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What is an API?

An API, or Application Programming Interface, is a way for different software or devices to communicate with each other. In networking, APIs allow network devices like routers, switches, firewalls, and controllers to share information or perform actions without needing someone to manually configure them.

For example, instead of logging into a router and typing multiple commands to check interface status, a network monitoring tool can use an API to request that information automatically. This saves time and reduces human error.

Examples of APIs in Networking

Here are some common ways APIs are used in networking:

• Network Monitoring: Tools like SolarWinds or Nagios can pull data from devices via APIs to show interface status, traffic statistics, or device health.

• Configuration Management: APIs let automation tools apply configurations across multiple devices at once. For example, updating VLAN settings on multiple switches.

• Cloud Networking: Platforms like AWS, Azure, or Google Cloud provide APIs to manage virtual networks, subnets, and firewalls programmatically.

• REST APIs on Network Devices: Many modern routers, switches, and firewalls support REST APIs to retrieve data or perform tasks, such as checking IP addresses or interface status.

Using APIs in networking makes management more efficient, allows automation, and gives a clear path toward network programmability.

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REST APIs and HTTP Methods

REST APIs are a type of API that use HTTP to communicate. They follow a set of rules that make it easier to manage data on network devices or monitoring tools. One way to understand how REST APIs work is through CRUD operations. CRUD stands for Create, Read, Update, Delete, and each action maps to an HTTP method.

• GET requests are used to retrieve information from a device. For instance, a network monitoring tool might use GET to pull interface statistics.

• POST requests are used to create new entries or configurations. For example, adding a new route on a router.

• PUT or PATCH requests update existing configurations. For example, updating the IP address of an interface.

• DELETE requests remove configurations or entries, like deleting a test VLAN.

These HTTP methods make it simple to interact with network devices programmatically. Instead of manually logging in to each device, you can send the right API request and get the job done automatically.

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HTTP Requests and Responses

When a network tool interacts with a device using a REST API, it does so by sending an HTTP request and receiving an HTTP response. Understanding these two parts is key to knowing how REST APIs work in networking.

HTTP Request

An HTTP request is what the client (like a network monitoring tool or automation script) sends to the network device. It usually includes:

• Method: Defines the action (GET, POST, PUT, DELETE)

• URL/Endpoint: The address of the device resource you want to access, like /interfaces or /vlans

• Headers: Extra information, such as authentication tokens or content type

• Body (optional): Contains data when creating or updating configurations (used in POST or PUT requests)

Example: A GET request to check interface status might look like:

GET /interfaces HTTP/1.1
Host: 192.168.1.1
Authorization: Bearer <token>

HTTP Response

After the device receives the request, it sends back an HTTP response. This response tells the client whether the request was successful and includes the requested data if applicable. A response usually contains:

• Status Code: Shows success or error (e.g., 200 OK, 404 Not Found, 403 Forbidden)

• Headers: Metadata about the response, such as content type

• Body: The actual data, often in JSON format, like interface names, statuses, or IP addresses

Example: A response for interface status could be:

{
  "interfaces": [
    {"name": "GigabitEthernet0/0", "status": "up", "ip": "192.168.1.1"},
    {"name": "GigabitEthernet0/1", "status": "down", "ip": "192.168.1.2"}
  ]
}

In networking, this allows automation tools to quickly retrieve or modify device information without manual configuration. Understanding requests and responses is the foundation for working with REST APIs on routers, switches, firewalls, and controllers.

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HTTP Response Classes and Status Codes

When a network device receives an HTTP request, it replies with an HTTP response. The response includes a status code that indicates whether the request was successful or if there was an error. Status codes are grouped into five classes:

Common status codes you’ll see in networking REST APIs:

• 200 OK – Request succeeded, data returned

• 201 Created – New configuration or object created successfully

• 204 No Content – Request succeeded, but no data returned (useful for DELETE or update requests)

• 400 Bad Request – The request was invalid or missing required data

• 401 Unauthorized – Authentication failed, invalid token

• 403 Forbidden – You don’t have permission to perform the action

• 404 Not Found – Resource not found (like an interface or VLAN)

• 500 Internal Server Error – Device encountered an error processing the request

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What is a REST API?

A REST API, short for Representational State Transfer API, is a way for network devices and management tools to communicate over HTTP. REST APIs follow a set of rules that make it easy to access and modify information on devices like routers, switches, firewalls, and controllers without logging in manually or using a device’s GUI.

In networking, REST APIs allow you to:

• Retrieve information: Check interface status, IP addresses, VLANs, routing tables, or device health

• Apply configurations: Create or modify VLANs, routes, firewall rules, and more

• Automate tasks: Scripts or tools can perform repetitive actions across multiple devices quickly

• Integrate with tools: Network monitoring, reporting, and automation platforms can pull or push data programmatically

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Key Principles of REST APIs

REST APIs follow several principles that make them simple and predictable:

1. Stateless Communication
   Each API request contains all the information the device needs. The device does not rely on past requests to understand the current one.

2. Client-Server Architecture
   The client (network tool, script, or monitoring platform) sends requests, and the server (network device) responds. This separation allows each side to evolve independently.

3. Resource-Based
   Everything the API interacts with is treated as a resource, like an interface, VLAN, or firewall rule. Resources are accessed through URLs (endpoints). For example:

    GET /interfaces
    GET /vlans
    POST /routes
   

4. Uniform Interface
   REST APIs use standard HTTP methods (GET, POST, PUT, PATCH, DELETE), making it easy to understand and use across different devices and platforms.

5. Representation of Resources
   Devices typically return data in a structured format like JSON, which is easy to read and process by scripts or tools.

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Why REST APIs are Important in Networking

REST APIs are becoming essential in modern networks because they:

• Enable Automation – No need to manually log in to multiple devices; scripts or tools can handle tasks automatically

• Reduce Errors – Automated requests reduce human mistakes that often happen during manual configuration

• Support Integration – Tools like network monitoring systems, configuration managers, and cloud platforms can easily communicate with devices

• Provide Scalability – Managing large networks with dozens or hundreds of devices becomes feasible

By understanding REST APIs, network engineers can move from traditional CLI-based management to automated, programmable networks, which is a key step toward modern network operations.

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REST: Client-Server

REST APIs follow a client-server model, which is the backbone of how devices and tools communicate in networking.

• Client: This is usually a network tool, script, or monitoring system that sends requests. The client asks for information or performs actions on the network device.

• Server: This is the network device itself, like a router, switch, firewall, or controller. The server receives requests from the client, processes them, and sends back a response.

Why it matters in networking:
By separating the client and server, REST APIs make networks easier to manage. The client doesn’t need to know how the server is built internally, it just sends a request to an endpoint and gets a response. Likewise, the server can handle multiple clients independently, making network management scalable and efficient.

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REST: Stateless

REST APIs are stateless, meaning every request from the client contains all the information the server needs to understand and process it. The server does not store any information about previous requests.

Example in networking:
If you want to check the status of an interface, the GET request must include the specific device and interface details. The server will respond based solely on that request. It doesn’t rely on any past interactions to process your query.

Benefits:

• Simplifies server design because it doesn’t need to track sessions

• Improves scalability, as each request is independent

• Reduces errors caused by relying on prior requests

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REST: Cacheable or Non-Cacheable

In REST APIs, responses can be cacheable or non-cacheable. This tells the client whether it can store the response for reuse or if it should always request fresh data from the server.

Cacheable:

• Data that doesn’t change frequently, like device model, firmware version, or VLAN configurations that are rarely modified

• Allows clients or network management tools to store the response and reduce repeated requests, improving efficiency

Non-Cacheable:

• Dynamic or rapidly changing data, such as interface status, traffic statistics, or current CPU/memory usage

• Clients must request fresh data each time to ensure they get the most accurate information

Why it matters in networking:
Caching helps reduce unnecessary load on devices and the network. However, using outdated information could lead to mistakes, like thinking an interface is up when it’s actually down. Knowing which responses can be cached ensures efficiency without compromising accuracy.

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Cisco DevNet: Learning and Using REST APIs

Cisco DevNet is Cisco’s developer program that provides tools, resources, and learning materials for network automation, APIs, and programmability. It’s a great starting point for network engineers who want to work with REST APIs and modern network management.

What DevNet Offers:

• Learning Labs: Step-by-step tutorials on using REST APIs with Cisco devices. You can practice tasks like checking interface status, updating configurations, or retrieving device information.

• Sandbox Environments: Virtual networks and devices you can access via REST APIs without needing physical hardware. This is perfect for testing and learning safely.

• API Documentation: Detailed guides for Cisco devices, showing endpoints, request formats, response examples, and status codes.

• Tools and SDKs: Software Development Kits (SDKs) and CLI tools to make it easier to interact with Cisco devices programmatically.

Why It’s Useful:

Cisco DevNet makes REST API learning practical. Instead of just reading about commands, you can send real requests to virtual devices, see responses, and understand how APIs work in a networking environment. It bridges the gap between traditional CLI-based network management and modern, automated networks.

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Summary

In this blog, we explored REST APIs from a networking perspective. We started by understanding what an API is and how it allows network devices and tools to communicate. We covered the key HTTP methods (GET, POST, PUT, PATCH, DELETE) and CRUD operations, showing how they map to common network tasks like checking interface status, creating VLANs, or updating firewall rules.

We also took a deeper look into HTTP requests and responses, including status codes and response classes, so you know how devices communicate and how to interpret their replies. Finally, we discussed the core REST principles: client-server architecture, stateless communication, and cacheable vs non-cacheable responses and highlighted Cisco DevNet as a practical platform to learn and test REST APIs in networking.

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Wrap Up

REST APIs are a key tool for modern network management. They simplify device interaction, reduce manual work, and enable automation across multiple devices. Understanding REST principles and HTTP methods allows network engineers to work more efficiently and manage networks programmatically.

Using resources like Cisco DevNet, you can practice REST API calls, explore real network data, and build skills that are essential for modern network automation. By embracing REST APIs, you can move from traditional, manual network management to a more automated, scalable, and reliable network environment.