Private networking creates a second network interface for Droplets that can only be accessed by the other Droplets and DigitalOcean Load Balancers in the same account or team. The private network is unreachable from the internet and traffic on it doesn’t count against bandwidth usage.
The DigitalOcean API lets you manage DigitalOcean resources programmatically using conventional HTTP requests. All the functionality available in the DigitalOcean Control Panel is also available through the API.
See the API documentation on private networking for Droplets for more information.
doctl is a command-line interface for the DigitalOcean API and supports many of the same actions.
doctl documentation on Droplets for more information.