GNS3 is described as 'graphical network simulator that allows simulation of complex networks' and is an app in the Education & Reference category. There are six alternatives to GNS3 for a variety of platforms, including Windows, Linux, Mac, Android and iPhone. The best alternative is Cisco Packet Tracer, which is free. Other great apps like GNS3 are Dynamips (Free, Open Source), NetSim (Paid), Eve-NG (Freemium, Open Source) and Free SNMP Agent Simulator (Freemium).
Packet Tracer is an essential learning tool used in these Cisco Networking Academy courses: IT Essentials, CCNA Routing and Switching, CCNA Security, Intro to Internet of Things (IoT), and Mobility Fundamentals.
NetSim for CCNP Network Simulator is now updated to support the new ROUTE, SWITCH and TSHOOT technologies. The improved interface of NetSim for CCNP makes completing labs, compiling new labs and designing network topologies easier than ever before. NetSim for CCNP 8.
The new EVE-NG platform is ready for todays requirements. It allows enterprises, e-learning providers/centres, individuals and group collaborators to create virtual proof of concepts, solutions and training environments.