Repository
https://github.com/GNS3/gns3-gui/releases
Introduction
If you are a computer network engineer or practising in its relating professions, you would have probably used a network simulator in the course of your study and work. It is something that is almost unavoidable except for a privileged few who have access to complete hardware devices from day one.
One of the advantages is that it is cheap (sometimes free), easy to set up and not everyone can afford a physical laboratory to test run networks.
In this post, I will be stating my personal experience using GNS3 (Graphical Network Simulator-3) for the computer network simulation. GNS3 is written in Python programming language and was first released in 2008. I will be discussing the challenges I faced setting up the application, suggestions or recommendations and comparing it with a proprietary competitor. An example of a proprietary software I have also used is Cisco's Packet Tracer. In order to be able to use it, you have to register for the Cisco Academy. Without a Cisco Academy account, in order to log in you would have to wait for a time countdown of 15 seconds.
Setting up GNS3
GNS3 is open source, free software that is readily available for download on the internet. The file size is less than 100 MB. The installation procedure is pretty straightforward and easy to navigate through. After downloading and installation, you don't just get to start using it immediately. You need to have the image file of the devices that you would be simulating (e.g Router, Switch). Sometimes the image files are not readily available for devices you seek.
When adding a router image to GNS3, there is a default RAM allocation of 192MB. But you can increase it to the level you want. After loading the images, the software is ready to use. There is no option for memory allocation on Packet Tracer
The Interface
The interface for both applications is both colourful and exciting. The interface of Cisco Packet Tracer is easier to navigate and use. All devices are easy to locate and are arranged with different models, all you need to do is simply drag and drop. Packet Tracer comes with nine different cable connections type, with an additional option to automatically select cable type. GNS3 automatically selects the cable. Cable connection type is an important knowledge for network engineers because the required connection for router-to-router is different from the connection for switch-to-router. When you constantly practice with an automatic option, you tend to forget the connection type and you might find it challenging in a real-life situation
GNS3 Usage and Experience
GNS3 does not require monthly or yearly fees. GNS3 is also multi-vendor, I use it for both my Cisco and Juniper certification exams and study. There are more images available for Cisco routers and switches than Juniper.
I use a personal computer with the 4th Generation Intel Core i5 with 8 GB of RAM and 1 TB of ROM. But when using GNS3, there is also a noticeable increase in the use of your computer memory. CPU usage can sometimes go above 50%. When using its counterpart Packet Tracer, CPU usage does not go beyond the 20 - 30% threshold. This might be a deciding factor for users whose computers do not have enough physical memory. There would likely go for the application with the lower resource needs.
With Packet Tracer, the command line code can be customized in different colours. Giving you a better feeling of the command prompt. On GNS3, you are stuck with the default black background and orange letters.
Backview of a router
Backview of a switch
Packet Tracer also comes with an option of not only viewing logical connection of devices but also the physical connection. With the ability to add additional modules to network devices like router and switches. This feature gives you a feeling like you are with the device in a real-life scenario. Many students who don't know how a device looks like can see it for themselves. You can also switch on and off the network device in the physical view. There have been reported cases in job test and interviews where potential employees could not physically recognize certain network devices. This option is not available on GNS3 software.
Packet Tracer is available on Microsoft Windows, Linux, Android and iOS meanwhile GNS3 is only available on Microsoft Windows and Linux. Packet Tracer is available in six languages giving it global flexibility. GNS3 comes with its own advantage of having over 800,000 community members and contributors
On a personal level, Packet tracer is easier to use but has limitations. I cannot use it to study beyond the introductory level of a Cisco certification (CCNA) meanwhile, the GNS3 can be used for study and practice up to the CCNP level of Cisco certification. This is so because some commands are not available. I remember reading one of the examination guides and trying to emulate some of the commands, I was just lost thinking I was the one at fault. Thinking probably I miss some pre-configurations. For the highest level of certification which is CCIE, physical hardware is strongly recommended.