Jithin Alex - Network Automation using Python 3: An Administrators Handbook

NETWORK AUTOMATION USING PYTHON 3 EDITION 1, 2018 Authored by: Jithin Aby Alex About the Author Jithin Aby Alex, CISSP, CEH Security Professional, having experience in implementing and handling major network security solutions and products in various environments and regions. I have used my experience, professional connection and publicly available information for writing this book. Personally I thank you for purchasing this e-book version and thanks for the support. I hope this book will be informative to you and I wish you all the best. Please visit www.jaacostan.com for my articles and technical write-ups. Copyright Jithin Aby Alex All Rights reserved.

No part of this publication may be reproduced, distributed or transmitted in any other form or by any other means including photocopying or any other electronic or mechanical methods without the prior written permission from the Author. Although the author have made every effort to ensure that the information in the book was correct at the time of writing, the author do not assume and hereby disclaim any liability to any party for any loss, damage or disruption caused by errors or omissions, whether such errors result from negligence, accident or any other cause. Kindle Edition. License Notes This e-book is licensed for your personal knowledge purpose only. This e-book may not be re-sold, re-write or given away to other persons. If you would like to share this book with others, please purchase and download through Amazon only.

Thank you for respecting the hard work of this author. Table of Contents

What is Network Automation?

Network automation is the process of automating the configuration, management and operations of a computer network. The tasks that were normally done by the network or system administrator can be automated using a number of tools and technologies. As we know, human errors is the number one reason for most of the issues including unavailability, downtime, security etc. in a network environment. A proper automation will eliminate the human errors and also speed up the operations, thus saving time and cost.

Network automation is implemented through the combination of hardware and software-based solutions that automatically execute repetitive tasks in a network environment. Scripting languages are widely used by Network and System administrators for automating the tasks. This saves time, effort and thereby reducing human errors as well. Among the automation tools, Python and Ansible are the most popular ones. With Software Defined Networking (SDN) in picture, knowing any of these programming languages is vital for the future of administering the network and systems.

How the book is written?

I wrote the book in a structured manner.

First get familiarize with the basics of python3 such as data types, lists, conditions, loops, libraries etc. Every concept is explained with examples. Once you get familiarized with the basics and concepts, lets get in to the real world applications of python3 in network administration. I have included many useful and practical examples that you might encounter in you daily administering tasks. Such as, changing configurations of multiple network devices, taking backup of multiple devices etc. in a single go using python3 script.

Feel free to revise the topics whenever you feel lost. Everything is written in simple language and I recommend you to practice each examples and exercises multiple times until you really understood the topics and concepts. I also encourage you to try writing the codes yourself. Practice keeps you in a better place. I wish you all the best.

Pre-requisites.

I assume those who are reading this book have a prior knowledge on IT networking especially with Cisco IOS.

Pre-requisites.

I assume those who are reading this book have a prior knowledge on IT networking especially with Cisco IOS.

There is no programming experience required for practicing the concepts referred in this book and for that reason, I have tried to explain all concepts from the basics itself. Note that, dont consider this book as a core python developer guide. This book is primarily intended for networking professionals on how to make use of python programming to automate their network administration tasks. If you want to do a deep dive on just the Python3 programming language, I recommend you to read the book Learn Python3 the hard way. https://learnpythonthehardway.org/python3/ Next, for practicing the network automation, either you should have some real network devices such as switches and routers, or you can practice it in GNS3 simulation software. In this book, I have explained the practicals using GNS3 virtual lab.

So from required software aspect, GNS3 and latest version of Python3 are the prerequisites.

Why Python?

One of the popular high level and easiest programming language which is used everywhere including software applications, the Web, operating systems etc. Also the resources related to python is available widely over the internet. - Easy to install - Readable and easy to understand - Large community support. The most widely implemented version of python is Python2. But Python3 is getting popular now and at present, most of the new applications and programs are written in Python3.

While writing the code, there is no big difference in Python3 compared to Python2. But, with future in mind, it is better to write the codes in python3.

How to Install Python 3?

In Linux python is usually comes preinstalled. For Windows OS, you can download python from the internet and install. 1) Install Python 3 Download python from the Python website. https://www.python.org/downloads/ To know more on how to install python on your machine, visit https://docs.python.org/3/using/windows.html 2) Verify the python is running in your machine.

Go to command prompt or shell, and type python. It will show the version installed. Use quit() or Ctrl-Z plus Return to exit

Setup path and environment variable

Once Python is successfully installed, specify environment variables if you want to execute python scrips from a specific path. This step is completely optional if you decide to execute the scripts from the python root directory only. Go to your system properties either from control panel or by right clicking My Computer and properties . Click on Advanced System Settings -> Advanced -> Environment Variables -> select python3 and click edit , and add a new path.

Here in this illustration, I have added a new path D:\Scripts . Which means I can execute the scripts in the folder directly using python3. You can specify the folder of your wish.

Important things to consider in python:

1) Indentation matters. Unlike other programming languages, Python considers Indentations and those spaces are very important. Improper indentation leads to error.

Python usually follows a 4 spaces indentation. I will be explaining about this in the coming chapters. Other Programming languages uses curly brackets {} for showing the code blocks, while python uses Indentation. import thi s command gives us a broad overview of Python3 in an easy readable way.