GNS3 Network Simulator

GNS3 (Graphical Network Simulator-3) is an open-source network software emulator that allows network engineers to build, design, and test complex network topologies by simulating routers, switches, firewalls, and other network devices. Developed by Jeremy Grossmann and Julien Duponchelle since 2008, GNS3 is widely used for CCNA, CCNP, and CCIE certification preparation and production network testing. Key features include: device emulation (run actual router and switch operating system images including Cisco IOS, Juniper JunOS, Arista vEOS, Fortinet FortiGate, Palo Alto, and VyOS providing realistic network behavior), Dynamips integration (emulates Cisco hardware platforms including 1700, 2600, 3600, and 7200 series routers with MIPS processor emulation), QEMU and VirtualBox (run full virtual machines including Linux routers and firewalls alongside emulated devices), Docker container support (run lightweight network appliances as Docker containers including FRRouting and openvswitch), VPCS (Virtual PC Simulator providing simple PC endpoints for testing connectivity with ping and traceroute), topology designer (graphical interface for creating network topologies with drag-and-drop device placement and link configuration), Wireshark integration (packet capture on any link for protocol analysis and troubleshooting), project management (save and load network topologies as portable project files with all device configurations), remote servers (distribute emulation workload across multiple GNS3 remote servers for larger topologies), appliance templates (pre-configured device templates for common network appliances), and exam preparation (industry standard tool for Cisco, Juniper, and HP certification practice).