In contrast to Packet Tracer, GNS3 is an emulator dedicated to anyone involved in computer networks. From students to network professionals, everyone can use GNS3 because it offers an easy way to design and build networks of any size without the need for hardware. And the best part is it is free!
However, you need to sign up (see Figure G.1) if you want to download it. To do so, navigate to https://gns3.com/software:
Figure G.1. Signing up for GNS3 download
Once you complete your signup and log in for the first time, you will be shown the download window, as shown in Figure G.2. Select your desired platform by clicking on the DOWNLOAD button.
Figure G.2. Downloading GNS3