When a user assigns a public IP address to an interface, the interface receives an IP address from a pre-determined range. The IP address is displayed in the lower-right corner of the Application design screen when the VM is started.
If a VM is restarted, the public IP might change. For a fixed IP address, the user uses an Elastic IP address, which remains with the VM as long as it is started.
Port Forwarding, on the other hand, uses the IP address of the public cloud provider where the Ravello hypervisor is deployed, and maps externally supplied services to arbitrary ports. For example, if the user defines an SSH service on port 22 of a VM and defines it as external, the actual port for accessing the service from outside could be 10000. When the VM is started, this port mapping or forwarding information is displayed in the lower-right corner of the Application design screen.