I only used GNS3 and Cisco Packet Tracer from the list when self-teaching CCNA. GNS3 installation shouldn't be that hard. On Windows just use the installation and fire up a VM in VBOX / HyperV (recommended) and it should automatically detect it. On Linux I have installed GNS3 using AUR package in ArchLinux, haven't tried on Ubuntu, but it should be straight forward. For the VM, you will need hypervisor setup (virt-manager, libvirtd) and KVM enabled. Most of the distrobutions should have its own kvm virtualization guide. You can also skip GNS3 installation on the host and just go to IP of the VM,so you can use beta Web UI where you can do most of the things you can do in GNS3 app. Good luck!
Hello networking community! I need a setup where I can forward my server from my private network to another network which has a public ip to forward the server itself to the internet. When a client connects to the server, traffic should get forwarded to my private network somehow. I know that's possible, but don't know how I can achive that.