Complete Guide to Netmiko Python Network Automation

In today’s era of rapid technological advancement, network automation is no longer a luxury - it’s a necessity. Organizations need their IT teams to manage complex network environments efficiently while ensuring robust security and scalability. Python libraries like Netmiko have emerged as game-changers in this space, offering simplified, secure, and multi-vendor network automation capabilities.

This article distills the knowledge shared in a comprehensive video tutorial on Netmiko. Whether you're an IT professional, part of a Managed Service Provider (MSP), or a network engineer in a startup or large enterprise, this guide will help you understand and harness the potential of Netmiko for network automation.

Why Netmiko? A Quick Overview

Netmiko is a Python library specifically designed for simplifying the configuration and management of network devices. Unlike the Telnet library, which is outdated, less secure, and cumbersome, Netmiko is built on Paramiko and leverages SSH (Secure Shell) for secure communications. Its multi-vendor support makes it highly versatile, compatible with devices from Cisco, Juniper, Fortinet, and Palo Alto, among others.

Key benefits of Netmiko:

• Secure data transfer via SSH encryption.
• Simplified syntax for configuration commands.
• Support for multi-vendor environments.
• Easier installation and usage compared to older libraries like Telnet.

Now, let’s dive into the step-by-step guide to using Netmiko for network automation.

Step 1: Preparing Your Environment

Before diving into coding, it's essential to set up your environment for seamless execution. Here’s what you’ll need:

1. Python Installed: Netmiko works with Python 3.x. Ensure Python is installed on your system.
2. Netmiko Library Installation: Install Netmiko using Python’s package manager, pip. Run the following command in your CLI:

   pip install netmiko
   

   If pip doesn’t work, use py -m pip install netmiko.
3. Text Editor: A code editor like Visual Studio Code (VS Code) will make scripting easier.
4. Networking Devices: Ensure you have access to network devices with SSH enabled. For Cisco devices, this includes:
   • Assigning an IP address to the device.
   • Enabling SSH by generating crypto keys (crypto key generate rsa).
   • Configuring login credentials and VTY lines for SSH access (line vty 0 4).

Step 2: Understanding Netmiko's Structure

Netmiko simplifies coding by reducing repetitive tasks. Here's the core structure of a Netmiko script for connecting to a device:

1. Importing the Library:
   Start by importing the ConnectHandler function from Netmiko.

   from netmiko import ConnectHandler
   

2. Device Dictionary:
   Define the target device's details in a dictionary format:

   device = {
       "device_type": "cisco_ios",
       "host": "192.168.1.1",
       "username": "admin",
       "password": "admin123"
   }
   

   Parameters:
   • device_type: Specifies the device's OS (e.g., cisco_ios, juniper, fortinet).
   • host: IP address of your network device.
   • username and password: Authentication credentials.
3. Connecting to the Device:
   Establish a connection using ConnectHandler:

   connection = ConnectHandler(**device)
   

4. Executing Commands:
   Send commands to the device using functions like send_command (for show commands) and send_config_set (for configuration commands). Examples:

   output = connection.send_command("show ip interface brief")
   print(output)
   

5. Disconnecting:
   Always disconnect after your task is complete:

   connection.disconnect()
   

Step 3: Dynamic Input for Flexibility

Hardcoding credentials in scripts isn’t ideal, especially in environments with multiple devices. Netmiko allows you to dynamically input device details at runtime. Use Python’s input() function for interactive prompts and getpass() for secure password inputs.

Here’s how to implement dynamic input:

from getpass import getpass

device = {
    "device_type": input("Enter device type (e.g., cisco_ios): "),
    "host": input("Enter device IP: "),
    "username": input("Enter username: "),
    "password": getpass("Enter password: ")
}

This approach enhances flexibility and security, especially in multi-device or multi-user environments.

Step 4: Configuration vs. Command Execution

Netmiko provides two distinct functions for interacting with devices:

1. send_command: For read-only commands like show running-config. Example:

   output = connection.send_command("show running-config")
   print(output)
   

2. send_config_set: For making configurations, such as creating loopback interfaces. Example:

   config_commands = [
       "interface loopback0",
       "ip address 192.168.1.1 255.255.255.0"
   ]
   output = connection.send_config_set(config_commands)
   print(output)
   

Netmiko intelligently handles mode transitions. For instance, when using send_config_set, the script automatically enters configuration mode, eliminating the need for manual steps like configure terminal.

Step 5: Saving Configurations to a File

Netmiko also enables you to save outputs to a local file for backup or compliance purposes:

output = connection.send_command("show running-config")
with open("running_config_backup.txt", "w") as file:
    file.write(output)

This script will create a text file named running_config_backup.txt containing the device's configuration.

Real-Life Use Case: Automating SSH Configurations

In the tutorial, a Cisco router was configured with the following steps:

1. Enable SSH on the router:

   line vty 0 4
   transport input ssh
   login local
   crypto key generate rsa
   

2. Use a Netmiko script to:
   • Create loopback interfaces.
   • Change logging buffer size.
   • Verify configurations with show ip interface brief.

These tasks were achieved with minimal code, showcasing Netmiko's simplicity and power.

Advantages of Netmiko Over Telnet

1. Security: Telnet transmits data in plaintext, exposing configurations to potential threats. Netmiko uses SSH, ensuring encrypted communication.
2. Ease of Use: Telnet scripts often require verbose commands and manual mode transitions. Netmiko automates these processes.
3. Modern Compatibility: Telnet libraries are deprecated in newer Python versions, whereas Netmiko is actively maintained.

Key Takeaways

• Netmiko is a powerful library for automating network configurations across multi-vendor environments.
• SSH-based security ensures encryption and compliance with modern security standards.
• Simplified commands reduce complexity, enabling faster deployment of network changes.
• Dynamic inputs improve flexibility, allowing scripts to adapt to different devices and scenarios.
• Netmiko’s multi-vendor support makes it adaptable for enterprises using diverse networking equipment.
• Use send_command for verification commands and send_config_set for pushing configurations.
• Save outputs to files for backups, audits, or compliance purposes.
• Transitioning from Telnet to Netmiko is essential for operational security and efficiency.

Conclusion

Netmiko is revolutionizing how IT teams and enterprises approach network automation. By combining simplicity, security, and scalability, it empowers organizations to manage their networks more efficiently while eliminating the risks associated with outdated Telnet-based protocols. Whether it’s automating repetitive tasks, multi-device configurations, or ensuring compliance, Netmiko is an indispensable tool for modern network engineers.

Start exploring Netmiko today to unlock seamless and secure automation for your network infrastructure!

Source: "NETMIKO library | Explained for Network engineers" - Network Geeks, YouTube, Sep 16, 2025 - https://www.youtube.com/watch?v=sGSu7TbjWbI