networksim is a free, browser-based network simulator and learning platform for designing topologies and testing security. Build a network with drag & drop, model firewall zones and ACLs, add IDS/IPS and load balancers, then run traffic-path tests, blast-radius analysis and N-1 resilience checks — no install and no sign-up required. It also includes 10 interactive, hands-on courses (VLANs, routing, firewalls, OSPF, redundancy and security) and troubleshooting challenges that teach networking from the ground up to advanced (CCNA) level.
Built for IT students, network engineers, security architects and homelabbers. JavaScript is required to run the simulator — please enable it and reload.
Browse the free networking courses and lessons