Network Programmability and Automation

581 Pages·2018·10.13 MB·English

by  Jason Edelman

Network
Programmability
and Automation
SKILLS FOR THE NEXT-GENERATION NETWORK ENGINEER
Jason Edelman,
Scott S. Lowe & Matt Oswalt

Praise for Network Programmability and Automation
Jason, Scott, and Matt have been key contributors in educating network engineers about
both network automation and Linux networking. They have written and talked
extensively about the importance of automation, on how automation impacts network
engineers, and on the mechanics of automating networking devices.
—Kirk Byers
Creator of the Netmiko Python Library
Network automation is no longer just a proof of concept: it represents both the present
and the future! Network Programmability and Automation provides the needed
background for modern engineers, by widening the toolset for more consistent, stable
and reliable networks.
—Mircea Ulinic
Network Systems Engineer, Cloudflare
Network automation is not hype anymore; it is a means to do your job faster, more
consistently and more reliably. However, network automation is not just a single
discipline; it is a collection of protocols, tools, and processes that can be overwhelming to
the uninitiated. This book does a great job covering everything you will need to get your
automation up and running.
—David Barroso
creator of NAPALM

Network Programmability
and Automation
Skills for the Next-Generation
Network Engineer
Jason Edelman, Scott S. Lowe, and Matt Oswalt
BBeeiijjiinngg BBoossttoonn FFaarrnnhhaamm SSeebbaassttooppooll TTookkyyoo
Network Programmability and Automation
by Jason Edelman, Scott S. Lowe, and Matt Oswalt
Copyright © 2018 Jason Edelman, Scott S. Lowe, Matt Oswalt. All rights reserved.
Printed in the United States of America.
Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472.
O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are
also available for most titles (http://oreilly.com/safari). For more information, contact our corporate/insti‐
tutional sales department: 800-998-9938 or [email protected].
Editors: Virginia Wilson and Courtney Allen Interior Designer: David Futato
Production Editor: Colleen Cole Cover Designer: Karen Montgomery
Copyeditor: Dwight Ramsey Illustrator: Rebecca Demarest
Proofreader: Rachel Monaghan Technical Reviewers: Patrick Ogenstad, Akhil Behl,
Indexer: Judy McConville Eric Chou, Sreenivas Makam
February 2018: First Edition
Revision History for the First Edition
2018-02-02: First Release
See http://oreilly.com/catalog/errata.csp?isbn=9781491931257 for release details.
The O’Reilly logo is a registered trademark of O’Reilly Media, Inc. Network Programmability and Automa‐
tion, the cover image, and related trade dress are trademarks of O’Reilly Media, Inc.
While the publisher and the authors have used good faith efforts to ensure that the information and
instructions contained in this work are accurate, the publisher and the authors disclaim all responsibility
for errors or omissions, including without limitation responsibility for damages resulting from the use of
or reliance on this work. Use of the information and instructions contained in this work is at your own
risk. If any code samples or other technology this work contains or describes is subject to open source
licenses or the intellectual property rights of others, it is your responsibility to ensure that your use
thereof complies with such licenses and/or rights.
978-1-491-93125-7
[M]
I dedicate this book to all network engineers starting their network automation journey.
I sincerely hope it provides each of you with the knowledge needed to further enhance
your career. I’d also like to thank Scott, Matt, and the whole O’Reilly team—I know it
was a much longer process than we all planned, but we ultimately got through it! Thanks
to everyone for making it a reality.
Jason Edelman
I’d like to dedicate this book to the Lord, who granted me the wisdom and understanding
I needed to write this book (Exodus 31:3 NIV). I’d also like to dedicate it to my wife,
Crystal, without whose support things like this wouldn’t be possible.
Scott S. Lowe
I dedicate this book to anyone with a hunger and a passion for learning—every word
was written with you in mind. I’d also like to thank my wife Jamie, who keeps me moti‐
vated and upbeat when life gets a little too crazy.
Matt Oswalt

Table of Contents
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
1. Network Industry Trends. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
The Rise of Software Defined Networking 1
OpenFlow 1
What Is Software Defined Networking? 5
Summary 16
2. Network Automation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Why Network Automation? 18
Simplified Architectures 18
Deterministic Outcomes 19
Business Agility 19
Types of Network Automation 20
Device Provisioning 20
Data Collection 23
Migrations 24
Configuration Management 25
Compliance 25
Reporting 26
Troubleshooting 26
Evolving the Management Plane from SNMP to Device APIs 28
Application Programming Interfaces (APIs) 28
Impact of Open Networking 32
Network Automation in the SDN Era 33
Summary 33
vii
3. Linux. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Examining Linux in a Network Automation Context 35
A Brief History of Linux 36
Linux Distributions 37
Red Hat Enterprise Linux, Fedora, and CentOS 37
Debian, Ubuntu, and Other Derivatives 39
Other Linux Distributions 40
Interacting with Linux 40
Navigating the Filesystem 41
Manipulating Files and Directories 46
Running Programs 52
Working with Daemons 55
Networking in Linux 60
Working with Interfaces 60
Routing as an End Host 71
Routing as a Router 75
Bridging (Switching) 77
Summary 83
4. Learning Python in a Network Context. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Should Network Engineers Learn to Code? 86
Using the Python Interactive Interpreter 88
Understanding Python Data Types 90
Learning to Use Strings 91
Learning to Use Numbers 100
Learning to Use Booleans 102
Learning to Use Python Lists 105
Learning to Use Python Dictionaries 111
Learning About Python Sets and Tuples 115
Adding Conditional Logic to Your Code 117
Understanding Containment 119
Using Loops in Python 121
Understanding the while Loop 121
Understanding the for Loop 122
Using Python Functions 126
Working with Files 129
Reading from a File 130
Writing to a File 132
Creating Python Programs 134
Creating a Basic Python Script 134
Understanding the Shebang 135
Migrating Code from the Python Interpreter to a Python Script 137
viii | Table of Contents