O'Reilly logo

Arista Warrior by Gary A. Donahue

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required


The examples used in this book are taken from my own experiences, as well as from the experiences of those with or for whom I have had the pleasure of working. Of course, for obvious legal and honorable reasons, the exact details and any information that might reveal the identities of the other parties involved have been changed.

Who Should Read This Book

This book is not an Arista manual. I will not go into the details of every permutation of every command, nor will I go into painful detail of default timers, or counters, or priorities, or any of that boring stuff. The purpose of this book is to get you up and running with an Arista switch, or even a data center full of them. What’s more, this book aims to explain Arista-specific features in great detail; however, it may not go into such detail on other topics such as explaining VLANs, routers, and how to configure NTP, since I’ve covered those topics at length in Network Warrior. I will go into detail if a topic is being introduced here that wasn’t covered in Network Warrior, such as Multiple Spanning Tree (MST), or VRRP. Where possible, I have concentrated on what makes Arista switches great. In short, if you want to learn about networking, pick up Network Warrior. If you want to know why Arista is stealing market share from all the other networking equipment vendors, buy this book.

This book is intended for use by anyone familiar with networking, likely from a Cisco environment, who is interested in learning more about Arista switches. Anyone with a CCNA or equivalent (or greater) knowledge should benefit from this book, but the person who will get the most from this book is the entrenched admin, engineer, or architect who has been tasked with building an Arista network. My goal in writing Arista Warrior is to explain complex ideas in an easy-to-understand manner. I’ve taught a few classes on Arista switches, and I see trepidation and fear of the unknown in students when the class begins. By the end of the class, I have students asking when Arista will go public, and if I can get them Arista T-shirts (I don’t know, and I can’t, but thanks for your emails!). I hope you will find this book similarly informative.

As I wrote in Network Warrior, I have noticed over the years that people in the computer, networking, and telecom industries are often misinformed about the basics of these disciplines. I believe that in many cases, this is the result of poor teaching or the use of reference material that does not convey complex concepts well. With this book, I hope to show people how easy some of these concepts are. Of course, as I like to say, “It’s easy when you know how,” so I have tried very hard to help anyone who picks up my book understand the ideas contained herein.

Let’s be brutally honest, most technology books suck. What drew me to O’Reilly in the first place is that almost all of them don’t. From the feedback I’ve received over the years since first writing Network Warrior, it has become clear to me that many of my readers agree. I hope that this book is as easy to read as my previous works.

My goal, as always, is to make your job easier. Where applicable, I will share details of how I’ve made horrible mistakes in order to help you avoid them. Sure, I could pretend that I’ve never made any such mistakes, but anyone who knows me will happily tell you how untrue that would be. Besides, stories make technical books more fun, so dig in, read on, and enjoy watching me fail.

This book is similar in style to Network Warrior, with the obvious exception that there is no (well, very little, really) Cisco content. In some cases I include examples that might seem excessive, such as showing the output from a command’s help option. My assumption is that people don’t have Arista switches sitting around that they can play with. This is a bit different than the Cisco world, where you can pick up an old switch on the Internet for little money. Arista is a relatively new company, and finding used Arista switches will probably be tough. Hopefully, by including more of what you’d see in an actual Arista switch, this book will help those curious about them.

Lastly, I’d like to explain why I wrote this book. I don’t work for Arista, I don’t sell Arista gear, and Arista has not paid me to write this book. Some time ago, a client had me do a sort of bake-off between major networking equipment vendors. We brought in all the big names, all of whom said something to the effect of, “We’re usually up against Arista in this space!” Because every one of the other vendors inadvertently recommended Arista, we contacted them, got some test gear, and went out to visit their California office.

I’ve been in IT for almost 30 years, and I’ve been doing networking for 25. I’m jaded, I’m grouchy, and I distrust everything I read. I’ve seen countless new ideas reveal themselves as a simple rehashing of something we did with mainframes. I’ve seen countless IT companies come and go, and I’ve been disappointed by more pieces of crappy hardware with crappy operating systems than most people can name. I’ve been given job offers by the biggest names in the business, and turned them all down. Why? Because big names mean nothing to me aside from the possibility of another notch added to my resume.

Nothing impresses me, nothing surprises me, and nothing gets past me. But when I walked out of Arista after three days of meeting with everyone from the guys who write the code to the CEO and founders themselves, I was impressed. Not only impressed, but excited! I’m not easily sold, but I walked out of there a believer, and in the short years since that first introduction, nothing has caused me to change my perception of Arista and their excellent equipment.

When I started writing, there were no Arista books out there. I felt that I could write one that people would enjoy, while doing justice to the Arista way of doing things. As you read this book, I hope that you’ll get a feel for what that way is.

Though I’m obviously a fan, these devices are not perfect. I’ll show you where I’ve found issues, and where there might be gotchas. That’s the benefit of me not being paid by Arista—I’ll tell it like it is. To be honest though, in my experience, Arista would tell you the very same things, which is what first impressed me about them. That’s why I wrote this book. It’s easy for me to write when I believe in the subject matter.

Enough blather—let’s get to it!

Conventions Used in This Book

The following typographical conventions are used in this book:


Used for new terms where they are defined, for emphasis, and for URLs

Constant width

Used for commands, output from devices as it is seen on the screen, and samples of Request for Comments (RFC) documents reproduced in the text

Constant width italic

Used to indicate arguments within commands for which you should supply values

Constant width bold

Used for commands to be entered by the user and to highlight sections of output from a device that have been referenced in the text or are significant in some way


Indicates a tip, suggestion, or general note


Indicates a warning or caution

Using Code Examples

This book is here to help you get your job done. In general, you may use the code in this book in your programs and documentation. You do not need to contact us for permission unless you’re reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing a CD-ROM of examples from O’Reilly books does require permission. Answering a question by citing this book and quoting example code does not require permission. Incorporating a significant amount of example code from this book into your product’s documentation does require permission.

We appreciate, but do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. For example: “Arista Warrior by Gary A. Donahue. Copyright 2013 Gary A. Donahue, 978-1-449-31453-8.”

If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at .

Safari® Books Online


Safari Books Online (www.safaribooksonline.com) is an on-demand digital library that delivers expert content in both book and video form from the world’s leading authors in technology and business.

Technology professionals, software developers, web designers, and business and creative professionals use Safari Books Online as their primary resource for research, problem solving, learning, and certification training.

Safari Books Online offers a range of product mixes and pricing programs for organizations, government agencies, and individuals. Subscribers have access to thousands of books, training videos, and prepublication manuscripts in one fully searchable database from publishers like O’Reilly Media, Prentice Hall Professional, Addison-Wesley Professional, Microsoft Press, Sams, Que, Peachpit Press, Focal Press, Cisco Press, John Wiley & Sons, Syngress, Morgan Kaufmann, IBM Redbooks, Packt, Adobe Press, FT Press, Apress, Manning, New Riders, McGraw-Hill, Jones & Bartlett, Course Technology, and dozens more. For more information about Safari Books Online, please visit us online.

How to Contact Us

Please address comments and questions concerning this book to the publisher:

O’Reilly Media, Inc.
1005 Gravenstein Highway North
Sebastopol, CA 95472
800-998-9938 (in the United States or Canada)
707-829-0515 (international or local)
707-829-0104 (fax)

We have a web page for this book, where we list errata, examples, and any additional information. You can access this page at http://oreil.ly/arista-warrior.

To comment or ask technical questions about this book, send email to .

For more information about our books, courses, conferences, and news, see our website at http://www.oreilly.com.

Find us on Facebook: http://facebook.com/oreilly

Follow us on Twitter: http://twitter.com/oreillymedia

Watch us on YouTube: http://www.youtube.com/oreillymedia


Writing a book is hard work—far harder than I ever imagined. Though I spent countless hours alone in front of a keyboard, I could not have accomplished the task without the help of many others.

I would like to thank my lovely wife, Lauren, for being patient, loving, and supportive. Thank you for helping me achieve another goal in my life.

I would like to thank Meghan and Colleen for trying to understand that when I was writing, I couldn’t play video games, go geocaching, or do other fun things. Thanks also for sitting with me for endless hours in Starbucks while I wrote. I hope I’ve helped instill in you a sense of perseverance by completing this book. If not, you can be sure that I’ll use it as an example for the rest of your lives. I love you both “bigger than Cozy” bunches.

I would like to thank my mother, because she’s my mom and because she never gave up on me, always believed in me, and always helped me even when she shouldn’t have. We miss you.

I would like to thank my father for being tough on me when he needed to be, for teaching me how to think logically, and for making me appreciate the beauty in the details. I have fond memories of the two of us sitting in front of my RadioShack Model III computer while we entered basic programs from a magazine. I am where I am today largely because of your influence, direction, and teachings. You made me the man I am today. Thank you, Papa. I miss you.

This book would not have been possible without the significant help from the following people at Arista Networks: Mark Berly, Andre Pech, Dave Twinam, Brad Danitz, Nick Giampa, Doug Gourlay, and Kevin McCabe. I’d also like to personally thank Jayshree Ullal, CEO of Arista, for allowing me access to some of the Arista equipment used for examples in this book. This book would simply not have been possible without all of your time and generosity.

A special word of thanks is needed for Mark Berly. I met with Mark many times, and probably emailed him 30 times a day for six months. It takes a special kind of person to tolerate me in the first place, but putting up with my nonstop questions takes someone who is either as nuts as I am, or who really loves the subject at hand, or both. Thank you for taking the time to answer my many hundreds of questions. This book would have sucked without your many helpful insights.

I would like to thank Craig Gleason for his considerable help with VMware and for putting up with my many ridiculous questions on the subject. The sections containing VMware references would not have been possible without your help and enthusiasm.

I would like to especially thank Glenn Bradley with his help designing and implementing my secret underground bunker. An entire chapter of this book would literally have not been possible without your help. You also get special recognition for finding an error in the 2nd edition of Network Warrior that made it through two editions, two technical editors, countless edits, and five years of public scrutiny. Not bad. Not bad at all.

I’d like to thank Bill Turner for always delivering what I needed without asking too many questions. May your cowboy changes never cause an outage.

Once again, I would like to thank Michael Heuberger, Helge Brummer, Doug Kemp, and the rest of the team in North Carolina for allowing me the chance to annoy and entertain them all on a daily basis. Oh, and Jimmy Lovelace, too; just because I know he’ll love to see his name here.

I would like to thank my editors, Mike Loukides for initially approving the project, and Meghan (with an h!) Blanchette, for dealing with my quirks on an almost daily basis.

I would like to thank all the wonderful people at O’Reilly. Writing this book was a great experience, due in large part to the people I worked with at O’Reilly. This is my third project with O’Reilly, and it just never stops being great.

I would like to thank my good friend, John Tocado, who hopefully by now already knows why. Thank you.

I still wish to thank everyone else who has given me encouragement. Living and working with a writer must, at times, be maddening. Under the burden of deadlines, I’ve no doubt been cranky, annoying, and frustrating, for which I apologize.

My main drive for the last few months has been the completion of this book. All other responsibilities, with the exception of health, family, and work, took a backseat to my goal. Realizing this book’s publication is a dream come true for me. You may have dreams yourself, for which I can offer only this one bit of advice: Work toward your goals and you will realize them. It really is that simple.

Remember the tree, for the mighty oak is simply a nut that stood its ground.

A Quick Note About Versions

When I started writing this book, EOS version 4.8.3 was the state-of-the art release from Arista. As I continued writing over the course of about a year, new versions of code came out. As a result, there are a variety of code revisions used in this book ranging from 4.8.3 to 4.10, which was released after the first draft of the book was finished.

While I would have loved to have gone back and updated all the examples to reflect the latest code, I simply ran out of time. Where there were significant changes or new features added, I made sure to use the latest code. In some cases, part of the chapter shows examples from one rev, while another part shows a different rev. I apologize in advance if this confuses anyone, but I really don’t think there should be any issues because the tech reviewers were great about pointing out where I needed to update my examples.

In my defense, the Arista team works so hard on releasing killer new versions of code that I had a hard enough time keeping up with new features, most of which I’m happy to say were included in this book. Hopefully, when I get to write Arista Warrior 2nd edition, I’ll get the opportunity to go through the entire book and update every example to the latest rev of EOS.

A Quick Note About Code Examples

In many of the examples involving code, I’ve had to slightly alter the output in order to make it fit within the margins of this book. I’ve taken great pains to not alter the meaningful output, but rather to only alter the format. For example, in the output of show top, the output includes lines that say something to the effect of:

last five minutes: 18.1%, last five seconds 3.1%.

In order to make the example fit, I might alter this to read:

last five mis: 18%, last five secs 3%.

Any changes I’ve made will in no way alter the point of the output, but the output may look slightly different than what you may see on your screen if you run the same command. In some cases, such as the output of tcpdump, I’ve simply changed the point in which the line wraps from, say, 80 columns to 70. Again, this should only have the effect of possibly making the output look different than what you would see when using a terminal emulator without such restrictions.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required