Starting with GNS3 2.0 a NAT node is available. This node allows you to a connect a GNS3 topology to the Internet via a NAT. But your topology is not accessible from the internet.

It’s useful when you need to download stuff from internet (package, licence check…). And it’s easier to use than the Cloud node.
The NAT node require the GNS3 VM or a Linux computer with libvirt installed. By default the NAT node run a DHCP server that will give you an IP in the range 192.168.122.0/24.

Free software worth $200: https://goo.gl/613TUF
VIRL image downloads: https://virl.mediuscorp.com/my-account/
Cisco IOS Software Download: https://software.cisco.com/download/home
GNS3 Download: https://gns3.com/
GNS3 Support (Go here if you need help): https://gns3.com/community