GNS3 - GNS3 is a graphical network simulator that allows simulation of complex networks.
Ansible - Radically simple configuration-management, application deployment, task-execution, and multi-node orchestration engine
ns-3 - a discrete-event network simulator for internet systems
Jenkins - Jenkins is an open-source continuous integration server with 300+ plugins to support all kinds of software development
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.
Puppet Enterprise - Get started with Puppet Enterprise, or upgrade or expand.