GNS3 is a Graphical Network Simulator that allows emulation of complex networks. GNS3 allows the same type of emulation using Cisco Internetwork Operating Systems. It allows you to run a Cisco IOS in a virtual environment on your computer.
We are going to be doing a lot of tutorials in the near future that will use GNS3 so the first logical step for you to follow along would be to install the software.
GNS3 also works on MacOS or Linux but today we are using Windows for handiness.
So let’s get started. You can download the GNS3 zip file with the link below.
Or visit here and do it this way.
GNS3 is free software under the GNU Public License. Next you will need to add some details about yourself. Fill in the fields and click on Create Account & Continue. Or login if you have already made an account.
Once you have done all that, the website will bring you to the download links. Click on the Windows Download if that is your operating system.
Once the download is complete click on Download again and the same window will appear. But at the bottom this time we notice download the GNS3 VM. Go ahead and click on that.
Now you have a choice to make. Which virtualization software do you want to use with GNS3? All three work fine but the one we normally use is VirtualBox, so we need to download that.
We will show you how to import the VM’s to GNS3 in later posts. So stay tuned for that. It allows us to import Docker images, which we might do. Let us know what you’d like to see.
Now let’s open up the GNS3 installer and install it on this PC.
With GNS3 during the installation it will give you some choices to install or not with the software. We will just keep everything default and click on next until we are asked to install.
Once you click on install let it do it’s thing. It will install various libraries and tools that GNS3 requires and can take some time to complete. You may be prompted by your antivirus to allow certain programs, you can go ahead and allow that.
If you got everything installed GNS3 will prompt you to create a new project. We just called ours LSB01, but you can name it anything you want.
If you did not get this far and GNS3 is giving you some trouble, do not fret, it is known to be buggy when first installed. Simply close the application and open it up again and this should work.
If everything worked for you then you will get the GNS3 GUI.
Give it a few moments to start the server and when you see the green icon beside the name of the laptop on the right hand side panel, then we know we are good to go.
Next we will set up a simple topology of a switch and 2 PC’s. This will be our virtual network. In the left hand panel click on the icon and just drag a switch into the main view panel.
Beautiful!! Now let’s do the same with VPCS, these are just virtual computers, drag and drop 2 into the panel.
Excellent, these devices will be perfect to get us started. Now all we need to do is connect them using virtual ethernet cables. So click on the and then click on PC1 and choose ethernet 0, then click on the switch and choose ethernet 0 also. This will connect those two devices.
Repeat the process for PC2 but use different interfaces, maybe choose ethernet1. Now we should be connected with virtual cables in our virtual network.
Well done, you have set up your first virtual network in GNS3, now all we need to do is give the PC”s an IP number to get connectivity between the two PC’s.
First we will need to hit the green play button at the top to boot the PC’s, because GNS3 simulates actual PC’s. Once they have started up we will open a console on both PC’s.
To open up a console on all devices click on the icon at the top. This will open up Solar Putty for us. This was installed with GNS3 in the original install.
Now that we have access to the consoles of the PC’s, let’s assign them and IP. On PC1 we will give it an IP of 10.1.1.1 and on PC2 we will give it 10.1.1.2 with the /24 submask.
ip 10.1.1.1 255.255.255.0
ip 10.1.1.2 255.255.255.0
If those commands went through for you without errors then we should have connectivity, so let’s ping PC2 from PC1.
Marvelous!! if you’ve followed along you should get pings from both PC’s to one another. It’s very important here to type save, to save the config, because GNS3 does not do that for you by default, so go ahead and do that.
We will be looking into hacking networks with GNS3 in future posts, like VLAN Hopping and Packet Injection, so stay tuned for those.
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Ciao for now!!
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