Dynamips

Dynamips is an open-source Cisco IOS router emulator that allows running Cisco IOS images on standard PC hardware. It enables realistic lab environments for learning, certification preparation, and network testing by reproducing the behavior of actual Cisco routers.

How it works: Dynamips simulates the hardware resources of Cisco routers by executing the router’s IOS image in user space on the host operating system. Each emulated router can expose Ethernet or serial interfaces mapped to the host’s networking stack, enabling the creation of complex topologies by interconnecting multiple devices. The software is typically used with front-ends such as Dynagen or GNS3, which provide configuration and management capabilities; GNS3 offers graphical integration and can also incorporate other emulation tools through plug-ins.

Supported devices and limitations: Dynamips supports a range of Cisco router families, including the 1700, 2600, 3600, 3700, and 7200 series images, subject to IOS licensing and hardware constraints. It is not a virtualization of physical hardware but a high-fidelity software model; performance depends on the host CPU speed and memory, and some IOS features or hardware-specific modules may be limited.

Licensing and usage: Cisco IOS images are proprietary, so users must supply their own IOS binaries to run with Dynamips. Dynamips is free and open-source software and has been widely used to build educational and testing labs, notably through its integration with GNS3.