Clients like the [GNS3 GUI](https://github.com/GNS3/gns3-gui/) and the [GNS3 Web UI](https://github.com/GNS3/gns3-web-ui/) control the server using a HTTP REST API.
* [uBridge](https://github.com/GNS3/ubridge/) is required, it interconnects the nodes.
* [Dynamips](https://github.com/GNS3/dynamips/) is required for running IOS routers (using real IOS images) as well as the internal switches and hubs.
* [VPCS](https://github.com/GNS3/vpcs/) is recommended, it is a builtin node simulating a very simple computer to perform connectivity tests using ping, traceroute etc.
* Qemu is strongly recommended as most node types are based on Qemu, for example Cisco IOSv and Arista vEOS.
* libvirt is recommended as it's needed for the NAT cloud.
* Docker is optional, some nodes are based on Docker.
* mtools is recommended to support data transfer to/from QEMU VMs using virtual disks.
* i386-libraries of libc and libcrypto are optional, they are only needed to run IOU based nodes.
Note that Docker needs the script program (`bsdutils` or `util-linux` package), when running a Docker VM and a static busybox during installation (python3 setup.py install / pip3 install / package creation).
The documentation can also be viewed [online](http://apiv3.gns3.net) however it may not be the most up-to-date version since it needs manually synchronization with the current code. Also, you cannot use this to interact with a GNS3 server.