How to integrate GNS3 with VirtualBox

The best method to test a solution that you want to implement is to real see how it’s performing with some real traffic. GNS3 or Dynamips are very good at emulating a network topology  but unfortunately they cannot assure you with the tools capable to test the environment you just create.

In one of my old posts I showed how to integrate Virtual PC with GNS3, but the problem is that with Virtual PC you can just test basic stuff. For example, you cannot simulate VoIP traffic with Virtual PC in case that you want to test some QoS marking and classification.

Here comes into play VirtualBox, a powerful x86 and AMD64/Intel64 virtualization product for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers, it is also the only professional solution that is freely available as Open Source Software under the terms of the GNU General Public License (GPL).

The integration on GNS3 with VirtualBox is not a hard thing to do, but you just have to be carefully in step implementation as if you skip one the solution will not work. For this solution I used Linux as host platform, so the steps works perfect under Ubuntu OS, but I’m sure that with some basic knowledge you can do it in Windows or MacOS.
Before we begin let’s summarize what you need:

Linux platform
VirtualBox installed
GNS3 installed

I assume that all 3 components are installed and working properly.  Next follow the steps below:

1. Bring up 2 or more (depending how many virtual OS you want to connect)  TAP interfaces on your Linux platform. I will go with 2 interfaces:
VirtualBox + GNS3 Step1

2. Configure the network interfaces of the Virtual OS in VirtualBox. I have 2 interfaces / Virtual OS. One interface is bounded to my physical network card (eth0) and I use this to connect to Internet in case that I need to download something, updates and so on… The second interface I use to connect to GNS3 virtual environment. Other settings of Virtual OS can be configured as you wish:
VirtualBox + GNS3 Step 2

3. Power on your Virtual OS Machines. In this moment if you didn’t bring the TAP interface up (Step 1), VirtualBox will issue an error and will refuse to start the Virtual Machines:
VirtualBox + GNS3 Step 3

4. Start GNS3 and build a network topology like the one in example below. You don’t have to follow exactly the same topology, but this is a good start to see that you are handling well the integration between Virtual Box and GNS3. In the example below and in regard to my Virtual Machine the Ubuntu-c = Uclient cloud and Ubuntu-s = Userver:
VirtualBox + GNS3 Step 4
5. Connect the routers R1 and R2 one to each other and to the Userver and Uclient clouds. On the routers the interface connection to cloud will be a (Fast)Ethernet and the clouds network interfaces have to be bounded to the TAP interfaces created on Step 1. Check in the images below how to do this:
VirtualBox + GNS3 Step 5

VirtualBox + GNS3 Step 5

In the end it should look something like this:
VirtualBox  + GNS3 Step 5
Now you should have an integration between GNS3 and VirtualBox. Please take into consideration the following advices before complaining that it’s not working:

– For end to end connectivity, you need to have a converged network. This means that you need to implement some kind of dynamic or static routing on your routers in order to have the end peers capable of reachability
-If you followed exactly my tutorial, and in Step 2 you configured 2 network interfaces per Virtual Machine, then you need to take care of the local IP routing. Usually in LAN network (with DHCP) the Virtual Machine interface bounded to the physical network interface will receive an IP address and also a default gateway. As an example, you can imagine that if you do no a have a static route on Userver pointing to R1 interface to reach Uclient, then all the packet will be forwarded to default gateway resulting in a issue in communication in virtual environment.
-Finally, take care when you configure the Clouds in GNS3 when assigning the TAP interfaces not to have a mismatch between Cloud – TAP interface – Router interface.

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