Table Of ContentMastering Python Networking
Third Edition
Your one-stop solution to using Python for network
automation, programmability, and DevOps
Eric Chou
BIRMINGHAM - MUMBAI
Mastering Python Networking
Third Edition
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First published: June 2017
Second edition: August 2018
Third edition: January 2020
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For my wife Joanna and children, Mikaelyn and Esmie.
For my parents, who lit up the fire in me many years ago.
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Foreword
This book you are holding in your hand or are reading on your screen has a power that
can be yours if you take time to study it. Much like Thor's hammer or Iron Man's suit,
programming is a superpower that amplifies your existing knowledge and skill set.
Many people feel, or are told, that they should learn programming and Python for
their own sake. Programming skills are in demand, so you should be a programmer.
That is probably good advice. But better advice would be to answer the question,
"How can you take your existing expertise and leap ahead of peers by automating
and extending that experience with software skills?" This book aims to do just
that for network professionals. You'll learn Python in the context of network
configuration, administration, monitoring, and more.
If you are tired of logging in and typing a bunch of commands to configure your
network, Python is for you. If you need to be certain that the network configuration
is solid and repeatable, Python is for you. If you need to monitor, in real-time, what
is happening on the network, well, you guessed it, Python is for you.
You are probably in agreement about learning software skills that can be applied
to network engineering. After all, terms like Software-Defined Networking (SDN)
have been all the buzz in the last few years. But why Python? Maybe you should
learn JavaScript or Go or some other language. Maybe you should just double
down on Bash and shell scripting.
Python is well-suited for network engineering for two reasons.
First, as Eric will demonstrate throughout this book, there are many Python
libraries (sometimes called packages) designed specifically on network engineering.
A focused search over at https://pypi.org for the network topic turns up over
500 different libraries for network automation and monitoring. With libraries such
as Ansible, you can create complex network and server configurations declaratively
using simple configuration files.
Using Pexpect or Paramiko, you'll be able to program against remote legacy systems
as if they had their own scripting API. If the gear you're configuring has an API,
chances are you can use a purpose-built Python library to work with it. So clearly,
Python is well-suited for the job.
Second, Python is special amongst programming languages. Python is what I
call a full spectrum language. My definition of this term is that it is both a language
that is incredibly easy to get started (print("hello world") anyone?) and also very
powerful, being the technology behind incredible software such as youtube.com.
This is not normal. We have solid beginner languages for quickly building software.
Visual Basic comes to mind here. So does MATLAB and other commercial languages.
Yet, when these are pushed too far, they fall down badly. Can you imagine Linux,
Firefox, or an intensive video game created with any of these? No way.
At the other end of the spectrum, we also have very powerful languages such as
C++, .NET, Java, and many others. C++ is, in fact, the language used to build some
Linux kernel modules and large open source software such as Firefox to some
degree. Yet, these languages are not beginner friendly. You have to learn about
pointers, compilers, linkers, headers, classes, accessibility (public/private), and
so on just to get started.
Python lives in both realms. On one hand it is incredibly easy to be productive
with just a few lines of code and simple programming concepts. On the other, it is
increasingly the language of choice for some of the world's most significant software;
such as that behind YouTube, Instagram, Reddit, and others. Microsoft chose
Python as their language to implement the command line interface (CLI) for Azure
(although you don't have to know or use Python to use their CLI, of course).
So, here's the deal. Programming is a superpower. It can take your network
engineering expertise and launch it into the stratosphere. Python is one of the
world's fastest growing and most popular programming language. Additionally,
Python has many highly polished libraries for working with networks in many
facets. This book, Mastering Python Networking, Third Edition, combines all of these
and will change the way you think about networking. Enjoy the journey.
Michael Kennedy
Portland, OR
Founder, Talk Python
Introduction
In 2014, I taught the first Coding 101 workshop on Python and REST APIs for
network engineers in the DevNet Zone at Cisco Live. The room was full of
prominent network engineers and architects, and many of them made their first
API call in this workshop. Since then, I have been honored to work with network
engineers from around the world who have decided to add coding to their skill set.
IT and Operations teams are changing. I believe the new normal will be network
engineers and software developers working side by side in the same team. The
scalability, complexity, and security that modern application deployments demand
from the network require automation to make network management repeatable,
reliable, and agile at scale.
Network engineers are problem solvers with deep expertise. Adding Python,
network automation, and API skills to the network engineering tool set creates
a powerful combination. With these added layers, engineers can approach problems
in new ways and tackle new types of challenges. Mastering Python Networking, Third
Edition is a valuable resource both for network engineers who want to learn coding
skills and for software engineers who want to take advantage of new programmable
infrastructure opportunities.
One of the questions that I often hear from engineers is, "Where do I start?" My
advice is: start simple. Look for challenges that your team faces, which are "read-
only," and focus on using automation to troubleshoot and gather information. You
can then use automation to flow the information that is gathered into ticketing
systems or chat applications, and soon you have started to build a workflow. This
safe-start, read-only evolution helps teams build confidence with automation and
familiarity with the tools.
At the beginning, focus on learning the core coding skills that will help you in every
project including Python coding and RESTful APIs and on using tools like Git and
GitHub to manage your source code and collaborate with others. Take the time to
set up your development environment. Try different code editors and tools such as
Postman and curl for exploring APIs. Build a solid understanding of how to work
with JSON and XML. Start exploring software development methodologies such
as test-driven development (TDD), and the core principles of DevOps.
Mastering Python Networking, Third Edition is a great resource for working on these
skills because it helps you learn these topics within the context of networking. The
book starts with using Python for basic network device interactions using CLI and
API, then moves up the stack with a general-purpose automation framework – all
from the perspective of network engineers. Along the way, Eric provides Python
examples on network security, monitoring, and constructing your own API with
the Flask framework. Eric also introduces networking in the cloud with both AWS
and Azure, as well as with common DevOps tools such as Git, Jenkins, and TDD.
Throughout the book, Eric explains topics using a pragmatic, practitioner-based
approach that helps you bring these concepts into your work.
DevOps and Cloud are transforming our industry. Development, operations,
security, and networking teams are connecting in new ways with shared goals
and responsibilities to deliver business outcomes. Network engineers who learn
software skills will help define this transformation.
So, find your first project and work on learning these skills in the scope of that
project. Pick something you do every day that you want to repeat reliably and
try to automate it. Get hands on and write code early and often. Build or find
a development lab where you can work. The more you can experiment, the
faster you will learn.
The innovations that are going to be created over the next five years by network
engineers and software engineers working together are going to be game-changing.
Take your first step, and don't forget to celebrate when you get your first 200 OK
successful API response.
Happy Coding!
Mandy Whaley
Senior Director of Developer Experience, Cisco DevNet
Contributors
About the author
Eric Chou is a seasoned technologist with over 20 years of experience. He has
worked on some of the largest networks in the industry while working at Amazon,
Azure, and other Fortune 500 companies. Eric is passionate about network
automation, Python, and helping companies build better security postures.
In addition to being the author of Mastering Python Networking (Packt), he is also
the co-author of Distributed Denial of Service (DDoS): Practical Detection and Defense
(O'Reilly Media).
Eric is also the primary inventor for two U.S. patents in IP telephony. He shares his
deep interest in technology through his books, classes, and blog, and contributes to
some of the popular Python open source projects.
I would like to thank the open source, network engineering, and
Python community members and developers for generously sharing
their compassion, knowledge, and code. Without them, many of the
projects referenced in this book would not have been possible. I hope
I had made small contributions to these wonderful communities in
my own ways as well.
I would like to thank to the Packt team, Tushar, Tom, Ian, Alex,
Jon, and many others, for the opportunity to collaborate on the
third edition of the book. Special thanks to the technical reviewer,
Rickard Körkkö, for generously agreeing to review the book.
Thank you, Mandy and Michael for writing the Forewords for this
book. I can't express my appreciation enough. You guys rock!
To my parents and family, your constant support and
encouragement made me who I am, I love you.
