Introduction to network automation with Python and Netmiko

Network automation involves automating the tasks of network devices such as switches, routers, and firewalls to improve efficiency and reduce errors. Python is a popular programming language used for network automation due to its simplicity and ease of use. Netmiko is a Python library used to automate network devices that support SSH connections.

In this article, we will provide an introduction to network automation with Python and Netmiko.

Setting up Python and Netmiko

To get started, you will need to install Python on your machine. You can download the latest version of Python from the official website (https://www.python.org/downloads/) and install it according to the installation instructions for your operating system.

Once you have installed Python, you can install Netmiko using pip, a Python package manager, by running the following command in your terminal:

pip install netmiko

Connecting to a Network Device with Netmiko

Netmiko supports various network devices such as Cisco, Juniper, and Arista. To connect to a network device using Netmiko, you will need to provide the IP address, username, and password of the device. For example, the following Python code connects to a Cisco switch using SSH and retrieves the device prompt:

from netmiko import ConnectHandler

device = {
    'device_type': 'cisco_ios',
    'ip': '192.168.0.1',
    'username': 'admin',
    'password': 'password',
}

connection = ConnectHandler(**device)

output = connection.find_prompt()

print(output)

Executing Commands on a Network Device

Once you have established a connection to a network device, you can execute commands on it using Netmiko. For example, the following Python code executes the show interfaces command on a Cisco switch and retrieves the output:

output = connection.send_command('show interfaces')

print(output)

You can also execute multiple commands on a network device using the send_config_set method. For example, the following Python code configures the interface speed and duplex of a Cisco switch:

config_commands = [
    'interface GigabitEthernet0/1',
    'speed 100',
    'duplex full',
]

output = connection.send_config_set(config_commands)

print(output)

Automating Network Tasks with Netmiko and Python

Netmiko and Python can be used to automate various network tasks such as device configuration, backup, and monitoring. For example, the following Python code configures the VLANs on a Cisco switch based on a YAML configuration file:

import yaml

with open('vlans.yml', 'r') as f:
    vlans = yaml.safe_load(f)

config_commands = []
for vlan_id, vlan_name in vlans.items():
    config_commands.append(f'vlan {vlan_id}')
    config_commands.append(f'name {vlan_name}')

output = connection.send_config_set(config_commands)

print(output)

The vlans.yml configuration file contains the VLAN IDs and names:

vlan1: default
vlan10: servers
vlan20: users

Building a serverless CI/CD pipeline with Python and AWS Lambda

Building a serverless CI/CD pipeline with Python and AWS Lambda can improve the speed and efficiency of your software development process. In this article, we will discuss how to build a serverless CI/CD pipeline using Python and AWS Lambda.

The components required for building a serverless CI/CD pipeline with Python and AWS Lambda include:

• AWS CodeCommit for source code management
• AWS CodeBuild for building and testing code
• AWS Lambda for automating the pipeline
• AWS CodePipeline for continuous delivery
• AWS CloudFormation for infrastructure deployment

import boto3
import json

def lambda_handler(event, context):
    codepipeline = boto3.client('codepipeline')
    try:
        response = codepipeline.start_pipeline_execution(name='my-pipeline')
        return {
            'statusCode': 200,
            'body': json.dumps('Pipeline execution started')
        }
    except Exception as e:
        return {
            'statusCode': 500,
            'body': json.dumps(str(e))
        }

Prerequisites

Before we begin, make sure you have Python installed on your system. You can download Python from the official website at https://www.python.org/downloads/. We will also be using some Python packages, so make sure you have the following packages installed:

pip: The package installer for Python.

virtualenv: A tool that creates isolated Python environments.

Setting up a Virtual Environment

The first step in getting started with Python DevOps automation is to set up a virtual environment. A virtual environment allows you to create a separate environment for your Python project, which can help avoid conflicts with other packages on your system.

To create a virtual environment, open a terminal or command prompt and navigate to the directory where you want to create your project. Then, run the following commands:

python3 -m venv myproject
source myproject/bin/activate

This will create a new virtual environment called myproject and activate it.

Installing Packages

Now that we have our virtual environment set up, we can install the packages we need for our project. In this example, we will install the requests package, which allows us to send HTTP requests from our Python code. To install the package, run the following command:

pip install requests

Writing a Simple Script

With our virtual environment and packages set up, we can now write a simple Python script to automate a task. In this example, we will write a script that sends an HTTP GET request to a website and prints the response.

Create a new file called get_request.py and add the following code:

import requests

url = 'https://www.example.com'
response = requests.get(url)

print(response.text)

Save the file and run it with the following command:

python get_request.py

This will send an HTTP GET request to https://www.example.com and print the response.

How to use Python for configuration management with Ansible

Ansible is an open-source configuration management tool that allows you to automate the provisioning, configuration, and deployment of servers and applications. Python is the language that Ansible is built upon, making it a natural choice for writing Ansible modules and playbooks. In this article, we will cover how to use Python for configuration management with Ansible.

Prerequisites

Before we begin, make sure you have Ansible installed on your system. You can install Ansible using pip:

pip install ansible

Ansible Modules

Ansible modules are reusable pieces of code that can be used to perform specific tasks, such as installing a package or configuring a service. Ansible comes with many built-in modules, but you can also create your own custom modules using Python.

To create a custom module, you need to create a Python file with a function that performs the task you want. The function should take parameters as input and return a JSON object as output. Here is an example of a custom module that installs a package using apt:

import subprocess
import json

def install_package(package_name):
    result = {}
    cmd = ['apt-get', 'install', '-y', package_name]
    output = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
    result['msg'] = 'Package installed successfully'
    result['output'] = output.decode('utf-8')
    return json.dumps(result)

Save this file as install_package.py in the directory where you want to run your Ansible playbook.

Ansible Playbooks

An Ansible playbook is a YAML file that defines a set of tasks to be executed on a set of hosts. Each task is defined as a module with parameters that define how the task should be performed. In the playbook, you can use the custom Python module we created earlier.

Here is an example of a playbook that installs a package using our custom module:

---
- name: Install package
  hosts: all
  become: true
  tasks:
    - name: Install package
      module: install_package
      args:
        package_name: nginx

Save this file as install_package.yml in the same directory as your custom Python module.

To run the playbook, use the following command:

ansible-playbook install_package.yml

This will run the playbook on all hosts defined in your Ansible inventory file.

Writing CI/CD pipelines with Python scripts and Jenkins

Jenkins is a popular open-source automation server that can be used to implement continuous integration and continuous delivery (CI/CD) pipelines. Python is a versatile language that can be used to write scripts to automate various tasks in the CI/CD pipeline. In this article, we will cover how to write CI/CD pipelines with Python scripts and Jenkins.

Prerequisites

Before we begin, make sure you have Jenkins installed on your system. You can download Jenkins from the official website at https://www.jenkins.io/download/. We will also be using some Python packages, so make sure you have the following packages installed:

pip: The package installer for Python.

virtualenv: A tool that creates isolated Python environments.

Setting up a Virtual Environment

The first step in writing CI/CD pipelines with Python scripts and Jenkins is to set up a virtual environment. A virtual environment allows you to create a separate environment for your Python project, which can help avoid conflicts with other packages on your system.

To create a virtual environment, open a terminal or command prompt and navigate to the directory where you want to create your project. Then, run the following commands:

python3 -m venv myproject
source myproject/bin/activate

This will create a new virtual environment called myproject and activate it.

Installing Packages

Now that we have our virtual environment set up, we can install the packages we need for our project. In this example, we will install the pytest package, which allows us to write and run tests in Python. To install the package, run the following command:

pip install pytest

Writing Python Scripts

With our virtual environment and packages set up, we can now write Python scripts to automate tasks in the CI/CD pipeline. In this example, we will write a script that runs tests using pytest.

Create a new file called test.py and add the following code:

import pytest

def test_example():
    assert 1 + 1 == 2

Save the file and run it with the following command:

pytest test.py

This will run the test and print the results.

Configuring Jenkins

Now that we have our Python script, we can configure Jenkins to run it as part of a CI/CD pipeline.

• Open Jenkins in your web browser and click on "New Item" to create a new project.
• Enter a name for your project and select "Freestyle project" as the project type.
• In the "Source Code Management" section, select your version control system and enter the repository URL.
• In the "Build" section, click on "Add build step" and select "Execute shell".
• In the "Command" field, enter the following command:

source /path/to/venv/bin/activate && pytest /path/to/test.py

pip install psutil

import psutil

# Get CPU usage
cpu_percent = psutil.cpu_percent()

# Get memory usage
memory = psutil.virtual_memory()
memory_percent = memory.percent

import logging

logger = logging.getLogger(__name__)

logger.debug('This is a debug message')
logger.info('This is an info message')
logger.warning('This is a warning message')
logger.error('This is an error message')
logger.critical('This is a critical message')

import logging

logger = logging.getLogger(__name__)
logger.setLevel(logging.INFO)

formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')

file_handler = logging.FileHandler('app.log')
file_handler.setLevel(logging.INFO)
file_handler.setFormatter(formatter)

logger.addHandler(file_handler)

logger.info('This is a log message')

2022-03-05 15:34:55,123 - __main__ - INFO - This is a log message

provider "aws" {
  region = "us-west-2"
}

resource "aws_instance" "example" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
}

terraform init

pip install python-terraform

import terraform

tf = terraform.Terraform(working_dir='./terraform')

tf.init()
tf.apply()

output = tf.output('public_ip')

print(output)

buckets = ['bucket1', 'bucket2', 'bucket3']

tf_code = """
provider "aws" {
  region = "us-west-2"
}

{}

"""

bucket_code = """
resource "aws_s3_bucket" "{}" {{
  bucket = "{}"
}}
"""

bucket_configs = [bucket_code.format(name, name) for name in buckets]

full_code = tf_code.format('\n'.join(bucket_configs))

with open('s3.tf', 'w') as f:
  f.write(full_code)

provider "aws" {
  region = "us-west-2"
}

resource "aws_s3_bucket" "bucket1" {
  bucket = "bucket1"
}

resource "aws_s3_bucket" "bucket2" {
  bucket = "bucket2"
}

resource "aws_s3_bucket" "bucket3" {
  bucket =

Please continue reading DevOps automation using Python - Part 2