Best answer by Matt Raio
One way is to use the VMNET and configure GNS3 in a couple of areas:
1. Your GNS3 server needs to be on the same subnet as your VMNET.
2. When you create a cloud interface inside the GNS3 topology, select the server IP address that is on the same subnet as the VMNET that Cumulus is on.
For any vm machine that is linux, check what the IP address is inside that VMNET by going to a command prompt and typing in ifconfig...
It's about the VMNET and either manually assigning an IP address or allow the DHCP service in the VMNET to assign one. Either way, both the GNS3 server and the Cumulus VM need to be on the same subnet and the VMWare VMNET will facilitate that.