This is my first article that will start off the networking section. I have not posted things in a while as I have been busy finishing my CCNA which I have already completed and I am currently working towards my CCNP.  I will go through the entire configuration to get Wireshark, Putty, GNS3, and VirtualBox configured for your virtual home lab on your windows computer(I might do a future article on getting this to work on Ubuntu which should be quite similar). I find that GNS3 is the best way to test out router/switch configurations if you don’t have any networking equipment available. There are a lot of things that GNS3 is capable of doing and it can emulate many different  Cisco platforms. Let’s go ahead and get started.

1. I start off by installing Wireshark even though there is a GNS3 version that has it integrated. I am not sure if GNS3 maintains the latest version of Wireshark on their package so I like to do it myself instead. See the screenshots below for a detailed step by step.







Note: make sure to install WinPcap


If you selected the WinPcap(you should unless you already have it installed) installation option then Wireshark will launch an installer for it.








2. Now that Wireshark is out of the way, the next step is to install PuTTY. I like to install PuTTY even though it comes integrated with GNS3 because I modify the settings on my version to personalize it to my taste. Note that I am using the windows installer for everything except  PuTTYtel since I used most of the applications included in the package. You can get PuTTY from here.







3. With PuTTY out of the way, I went ahead and downloaded the 64 bit standalone version of GNS3 from their website. I extracted the package and put the directory under my “Program Files” directory.



4. Now that we have GNS3 installed let’s go ahead and launch it to test that it is installed properly as well as to configure it.


Hit cancel on the new project screen


Head over to the preferences by clicking edit at the top


Under the GUI Settings I checked the two top settings as I find that it helps when using GNS3.


In the terminal Settings flags I modified the path to point to my version of PuTTY that I installed earlier.

Note: I removed the “wt” flag that was part of the command because the default putty version does not recognize it. This flag is responsible for changing the title of the window when you launch it from GNS3.


Head over to the Dynamips section and select “Test Settings” at the bottom


Hit allow access if prompted by windows


Verify that it passed successfully


Head over to the capture section and confirm your Wireshark settings.


The last thing that we will do for now is to test the Qemu settings and you should have similar results to what I got from the screenshot above.

5. The next that we have to do is to configure our Cisco IOS Images in GNS3. By default GNS3 will want to use the path “C:\Users\YourAccount\GNS3\Images\” for the IOS image directory. You can change this by going to Edit–>Preferences–>General–>General Settings. I have put all my images in the GNS3 directory since it suits me fine.

Note: Do not ask me for Cisco IOS images as I will not give them to you. Contact your Cisco representative if you need them.


6. Head over to edit–>IOS Images and Hypervisors–> in GNS3 and browse to one of our .image files(you might have .bin files instead). The .bin files are compressed and take longer to load and if you choose one of these files GNS3 will prompt you to extract it into an image file. Go ahead and do so as the image will load quicker on your devices than the .bin as it doesn’t have to extract it before hand.

I am using an advanced enterprise services image for a 3725 model which supports all the features that I will need for CCENT/CCNA/ and CCNP. In the near future I will be getting some real equipment for my home lab and will make a detail post about the devices that I chose.



Hit save when done and ignore the IDLE PC value at the bottom. I will show you how to configure this next.

7. Let’s go ahead and calculate the idle PC value by placing a router on our main window.


Before powering on the device you want to go ahead and configure it by right clicking it and choosing the configure option.


GNS3 recommends that you add one of the following adapters to your device:


If you don’t have any of the above then go ahead and choose anything else.


Hit apply when done and go ahead and start your router.


Once your router has started open a console to it by right clicking and selecting console.


Make sure that you are in enable mode and that you have the “#” prompt.


If your router has finished loading the next step is to right-click on the device and select idle PC which will go ahead and calculate idle PC values for our device. This means that when the router is sitting idle it will not consumer CPU resources because otherwise you will notice that you CPU will spike even though the router is not processing anything.


You will be presented with a new windows from which to choose idle PC values. As the windows states, values that are marked with a * are better. See below for the utilization of my CPU after selecting an idle PC value for my router. Notice how the utilization drop to 3% from around 25%.


You can verify that the idle PC value applied properly by heading back into the IOS Images and Hypervisors window and checking that your device has a hexadecimal address for its idle PC value.


8. The last component that we need to install is VirtualBox which will allow us to connect virtual machines to our networking gear instead of using loopback interfaces to test for connectivity. See the screenshots below for a detailed step by step on the VirtualBox setup.



Select all the components.





Select install on the different windows security warnings that will pop up.





Select install one more time.


You should be all done.


Let’s head back into GNS3 and verify that VirtualBox was successfully installed be heading over to our preferences–>VirtualBox and hitting test settings at the bottom.


I will be using a Windows XP VM that I used for testing purposes to demonstrate the rest of the configuration. We want to add two virtual adapters to our VM because one of the interfaces will be used for management by virtual box and the other by GNS3. In VirtualBox we want to go over to File–>Preferences–>Network and hit the add button to add another adapter.


Once the adapter is finished creating head over to the VM that you will used with GNS3 and modify its network settings. Enable both adapter 1 and adapter 2 and make sure that they are set to “Host-only Adapter”. Uncheck the cable connect option at the bottom for both adapters and make sure that you map each adapter to its own VirtualBox Host-Only Ethernet Adapter.


Back in GNS3 you want to head back to your preferences and select VirtualBox. Head over to the VirtualBox Guest tab and hit “refresh VM List”. You should see your VM in the drop down list and you can select it and give it a name. Make sure that the number of NICs is set to 2 and save when you are done.


We can now test our VM by dragging it to our workspace and connecting it to a router. Make sure that you are able to power both of them on.


This concludes this article and I hope that it was informative. In a future article I will walk you through a basic configuration to verify that everything works as well as some basic packet capturing with Wireshark for demonstration purposes. That is it for now, thank you for taking your time to read this post. See you around next time.

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