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Packing Light: Thin Provisioning with GNS3 and NPM

Level 17

In the nearly three decades I've worked in IT, there is a truth that trumps all others: More is better; smaller is better; and more-into-smaller is the best.

Whether your area of interest is storage, DevOps, virtualization, networking, app dev, or InfoSec, squeezing more into a smaller footprint (bits, lines of code, CPUs, etc.) is always better.

The ultimate expression of this is the Hollywood fantasy hacker. This is the computing wizard who steps onto the scene with little more than an average looking laptop, flips it open, and immediately begins bending the systems in question to their will. This magical notebook apparently is outfitted with infinite disk, thousands of CPUs, which can process millions of instructions per second, and connectivity that would put Google® Fiber to shame. If needed, it can spawn dozens of guest instances and mimic routers, load balancers, and firewalls.

Of course, that's just a fantasy. But it's one borne of a very real desire in the hearts and minds of IT professionals all over the world. The ability to create a realistic virtual simulation of a real computing environment, whether for testing, modeling, historical reference, or hacki... I mean penetration testing, is a very real need that often goes unmet in businesses today.

I bring this up because each day we seem to be getting closer to making this a reality. With tools like VMware® and VirtualBox®, we can now carry an entire server farm in our knapsack (as long as we have enough CPU and RAM). But, until recently, the network still eluded those who wanted to create a realistic simulation of their environment, including servers and network devices.

GNS3 has been the go-to option for simulated networks for years, but the primary use was preparing for certification exams. Then, about a year ago, GNS3 introduced the ability to link virtual machines (desktops or servers) to those network devices.

Suddenly, it became possible to not only model the network, but the servers behind those networks as well. We could simulate Active Directory® traffic, watch Web requests traverse the network, hit the load balancers and return to the requesting PCs. We could even test out monitoring.

Obviously, it's that last item that caught my attention. With this new ability to simulate both networks and servers, you could set up a polling engine, monitor the whole shebang, and test out scenarios like parent-child logic, routing failures, detecting configuration changes, and more.

GNS3 even put together a quick-start guide to help users set up SolarWinds® NPM. But this guide overlooked some key challenges:

  • Many members of the SolarWinds community are unfamiliar with setting up networks from scratch. They inherit them, monitor them, and even troubleshoot issues. But setting it up from scratch is often outside their skill set.
  • Many members of the GNS3 community are unfamiliar with monitoring tools in general, and SolarWinds® NPM specifically. So the details of configuring the server, running discovery, and setting up alerts is outside their skill set.

This is why I took the plunge and created a guide that helps both groups.

You can find it here:

It's really two guides in one. For those IT pros who are new to networking, the first half explains how to install GNS3 and then set up a simple three-router network. The second half is for network engineers who want to get SolarWinds NPM set up quickly without any of the false starts that comes with setting up a server application when you prefer to spend your day working with the bottom three layers of the OSI model.

Once you are set up, you will be well on your way to striding into the room, flipping open your magic laptop, and exclaiming, “My simulation shows we’ll be down to 27.3% network cohesion in just under 30 minutes!”

Then you can begin typing frantically, and save the day.


Nicely done!

I agree, Moore's Law rocks, and we all benefit from faster, smaller, less expensive.

At first I thought "The Matrix" movies had it right, but in the last couple of years I've heard that the futurists are predicting what we do online or wirelessly today, we'll do with a combination of hardware, software, and wetware tomorrow.  In twenty years, it's said, we'll have wireless network connectivity within our bodies which will enable us to do the communicating, controlling, and entertaining that we use wired connections for today.

Of course ethics and morals and security concerns will only grow.

But at least folks like adatole‌ are being forward-thinking enough to cover the bases for the folks who are inheriting or just learning networks.

Good one, Leon!

Level 17

One of the benefits of being an MVP and contributor is that you get to see content "early". However, I never thought anyone really DID. You sir, get 1million "Leon" points for your diligence, interest, and support.

Unfortunately that won't help you beat aLTeReGo‌ on the Thwack board, but it ranks you very high on my personal esteem list!

Leon, aLTeReGo‌ rocks most extremely and in high style, but a million Leon points still sounds pretty fine to me.  I'll never catch up to those top tier experts, but I enjoy sighting in on the next person up the points ladder and doing what I can to advance to their level--or beyond. 

MVP sounds mighty nice, too.  Maybe soon . . .

Level 13

aLTeReGo has several years ahead of most in the community seeing as how he was using the product before SolarWinds was a household name, but I have to agree that he rocks!

I like your handle better than most.  Clever and ironic and intuitive, all in one blow.  Efficient!


Most excellent adatole‌ !!

rschroeder Those Leon points are fleeting and priceless as they are not indicated anywhere...

This is so good, adatole‌! If I had access to IOS images, I can assure you this would be bookmarked well into the future. It would make life much easier when we migrate from one provider to another.

Well done.

Level 17

THank you for the kind words. I will say that IOS images are not that difficult to come by. Especially the common ones like the one I used in this guide.

The info just keeps getting better....


Level 9

This is incredibly awesome. I've been meaning to check on GNS3 for a few months now - this is perfectly timed for my personal workload. I just need to carve out some time and have some fun. I've scanned through the document and it looks great. Two big thumbs up!

Level 17

I'm really glad this helped you out at the right time! Report back and let us know how the guide worked for you. If there's a way to improve it, I want to know!

Level 14

Great paper!  I have already pulled it down and sent it out to our networking team.

Level 9

Great post. Been using GNS3 for years, but hadn't really thought about using NPM with it. Hmmm...

"rschroeder: In twenty years, it's said, we'll have wireless network connectivity within our bodies which will enable us to do the communicating, controlling, and entertaining that we use wired connections for today."

How do we secure wetware? That thought will most likely keep me up tonight.

buglovin‌, I've no idea.  "Just say 'no' to web implants/mind control/Thought Police and Brain Hackers?"

Black I.C.E. (Intrusion Counter Electronics--from cyber punk novel "Burning Chrome"--an excellent story about a pre-Matrix environment).  Black ICE is fiction, but is used against wetware that breaks rules.  Think of trying to hack the NSA and running into distributed powerful networks with strike back capabilities, which send electric current into hackers' minds and fry 'em.

Level 9

Terrifying and exhilarating.

I'm going back to a flip phone.

Level 9

Excellent Guide.  I have been running GNS3 off and on for a number of years so can highly recommend it myself.  However, in the past I had lots of trouble with running it on Windows and seemed to always encounter performance issues and bugs that never appeared to plague the Debian Linux derivatives like Ubuntu or Mint.  The good news is that the GNS3 team has done a lot to address these issues but I still prefer to run it on Linux.  I've linked a couple of guides for installation instructions under Ubuntu & Mint that will only need minor modifications to address version releases.  I found both these guides very thorough and complete with regard to getting all the needed dependencies installed.  I also found KDE's Konsole to be the best tabbed terminal emulator for console and telnet/ssh access.

One more thing.  If you want a good entry level book I would take a look at "THE BOOK OF GNS3" by Jason Neumann.  It is fairly entry level so many of the topics I had already struggled through however there were some really helpful articles such as setting up a client/server environment in GNS3.  The below link has a 30% discount code.  Best of luck in your GNS3 travels.

Community Blog: Q+A w/ The Book of GNS3 Author ... | GNS3

HOW TO Install GNS3 1.3.7 on Linux Mint 17.1 Re... | GNS3

HOW TO Install GNS3 1.3.7 on Ubuntu 14.04 LTS 6... | GNS3

Thanks for a great article, I'm just in the process of setting this up now, got to figure out how to simulate multihomed ip transit. HMMMM

Level 10

hey adatole‌  The link for the doc doesn't work.  Can you post a new link or otherwise make the docs available?  I've got some t-shirts to earn. 

Level 13
Level 10

Thanks mrs.alterego‌!

Level 14


Nice! There's just no better word to describe it. I've been using GNS3 for <ahem...> "years." I have to admit, like SW, GNS3 has come a long way. Maybe SW should "assimilate" it and provide it as a free product? Or assimilate it and provide functionality for NTM. Now that's a product I would not be able to live without! That would be a great competitor to NetBrain.

Another cool tool that was recently born, Cisco VIRL. It's another simulator but has an annual subscriptions fee.   This provides NX-OS ability, but doesn't provide the VM ability (pro/con).


Level 17

Those are some cool ideas. Luckly, they don't let me anywhere near the checkbook (or the people who control said checkbook) so I can't say I could DO anything about it. But it's an interesting idea!

To everyone else: what would YOU do to extend GNS3 functionality?

About the Author
In my sordid career, I have been an actor, bug exterminator and wild-animal remover (nothing crazy like pumas or wildebeasts. Just skunks and raccoons.), electrician, carpenter, stage-combat instructor, American Sign Language interpreter, and Sunday school teacher. Oh, and I work with computers. Since 1989 (when you got a free copy of Windows 286 on twelve 5¼” floppies when you bought a copy of Excel 1.0) I have worked as a classroom instructor, courseware designer, desktop support tech, server support engineer, and software distribution expert. Then about 14 years ago I got involved with systems monitoring. I've worked with a wide range of tools: Tivoli, Nagios, Patrol, ZenOss, OpenView, SiteScope, and of course SolarWinds. I've designed solutions for companies that were extremely modest (~10 systems) to those that were mind-bogglingly large (250,000 systems in 5,000 locations). During that time, I've had to chance to learn about monitoring all types of systems – routers, switches, load-balancers, and SAN fabric as well as windows, linux, and unix servers running on physical and virtual platforms.