DigitalOcean Reserved IPs are publicly-accessible static IPv4 addresses. Assign and reassign reserved IP addresses to Droplets as needed, or implement an automated failover mechanism with reserved IPs to build a high availability infrastructure. IPv6 support is now available in public preview. Enroll in the feature preview to create reserved IPv6 addresses.
All reserved IPs are free when assigned to a Droplet.
Reserved IPv4 addresses cost $5.00 per month ($0.01 per hour) when reserved but not assigned to a Droplet, due to the shortage of available IPv4 addresses. You are not billed unless you accrue $1 or more per reserved IP.
Reserved IPv6 addresses (currently available in public preview) are free even when not assigned to a Droplet.