A DigitalOcean Reserved IP address is a publicly-accessible static IP address that you can assign to a Droplet and then reassign to another Droplet later, as needed. You can implement a failover mechanism with reserved IPs to build a high availability infrastructure.
Reserved IPs let you redirect network traffic between any of your Droplets within the same datacenter. Assigning a reserved IP to a Droplet doesn’t replace or change its original public IP address.
You can use reserved IPs to create server infrastructures without single points of failure, but a reserved IP alone does not automatically provide high availability. For a setup to be highly available, you need to implement a failover mechanism to automate the process of detecting failures of the active server and reassigning the reserved IP to a passive server.
You can manage reserved IPs with the API for automatic reassignment.