GNS3 - GNS3 is a graphical network simulator that allows simulation of complex networks.
ifttt - IFTTT puts the internet to work for you. Create simple connections between the products you use every day.
ns-3 - a discrete-event network simulator for internet systems
Zapier - Connect the apps you use everyday to automate your work and be more productive. 1000+ apps and easy integrations - get started in minutes.
NetSim - NetSim software was created to simulate various Cisco systems. Cisco software is known around the world as being one of the best network, routing and switch systems for businesses and private use. Read more about NetSim.
n8n.io - Free and open fair-code licensed node based Workflow Automation Tool. Easily automate tasks across different services.