I have been looking for an alternative of Cisco Packet Tracer for a long time. The Cisco Packet Tracer is a good tool for network simulation, but it is not cross-platform, and there are few images to select. GNS3 looks like a great replacement with neat and modern UI, wide range of appliances and cross-platform support.
One feature of GNS3 I like is that it separates the GUI with its simulation environment, so instead of installing tons of dependencies and runtime, one can work with the network schema in the GUI and throw all simulation work to another machine. Although it is fine install the GNS3 server on the bare system, I prefer running everything in the VM/container for better isolation and management.
GNS3 officially supports many visualizations such as VirtualBox, VMWare, KVM and Hyper-V. I choose KVM in Linux.
On Debian flavor distro:
Shut down all running VMs and unload the
Activate the nesting feature (temporarily, restore default after reboot)
Activate the nesting feature persistent between reboots, edit
For AMD processors, replace
amd in the above commands,
GNS3.VM.KVM.*.zip from GNS3 GitHub repo
Unzip the file and create the VM using two disk image.