Reserved and Floating IPs

A reserved IP and a Floating IP are the same thing underneath: a public IPv4 address that belongs to your account. What differs is how many resources hold it at once, and so what you use it for.

A reserved IP moves between resources

Once you reserve an address, it is no longer tied to one resource. You can attach it to a node as its primary public IP, or to a node or a firewall as an Add-on IP next to the address it already has. Detach it and it is still yours, ready for the next resource, until you delete it.

That makes a reserved IP the right choice for anything that remembers your address: a DNS record, an allow list at a partner, a client set up with a fixed IP. You can replace the node behind the address and none of them need to change.

A Floating IP is shared by several nodes

A Floating IP is a reserved IP switched into a mode where up to four nodes on the same network hold it at the same time. The address answers on one of them at a time. Software on the nodes, such as Keepalived, decides which, and moves the address to another node when that one fails, so clients keep using the same IP.

Use a reserved IP when one resource at a time needs the address. Use a Floating IP when two or more nodes run the same service and it must stay reachable when one of them fails.

Switching to a Floating IP

You turn an Available reserved IP into a Floating IP with Use as Floating IP. The switch is one way: the address stays a Floating IP until you delete it, and you attach and detach nodes as often as you like in the meantime. See Use a reserved IP as a Floating IP.

What each status means

• Available: reserved to you and attached to nothing. Only an available address can be attached as an Add-on IP, converted, or moved.
• Attached: in use as a primary IP, an Add-on IP, or a Floating IP. Detach it before you delete it.
• Unavailable: you reserved the public IP of a resource that is still running and still uses it. It becomes Available once that resource is deleted.

For how these addresses sit alongside a node’s own public and private IPs, see Public and private IPs on a node.