GNS 3

First launched in 2008, GNS3 is a free and open-source network simulation software. It can run real IOS images and built based on Dynamips and QEMU. Network engineers all across the world use GNS3 to configure, test, and troubleshoot real and virtual networks. Cisco, Docker instances, Linux switches, and virtual machines running either Windows or Linux are all supported by the program. GNS3's ability to virtualize real hardware components without the need to purchase expensive hardware is one of its key benefits.