Use a reserved IP as a Floating IP

A Floating IP is one public address shared by up to four nodes, so a service keeps the same address when the node behind it fails. Here you turn a reserved IP into a Floating IP and choose its nodes.

Before you begin

• A reserved IP with the status Available.
• One to four nodes on the same network. Two is the usual start: a primary and a backup.

The switch is one way: from then on the address works as a Floating IP until you delete it.

Convert the IP

1. Open Network > Reserve IP.
2. Open the address’s Actions menu and choose Use as Floating IP.
3. Select your nodes, then click Convert.

The type changes to Floating IP and the status to Attached, with the nodes listed under Assigned To.

The address starts answering once one of the nodes claims it, and failover software such as Keepalived does that for you. Set up failover with a Floating IP walks through it.

Add or remove nodes

To add a node, open the address’s Actions menu, choose Attach IP, and pick the node. A Floating IP holds up to four.

To remove nodes, choose Detach IP, remove the nodes you want to take off, and click Detach IP. If the node runs Keepalived, stop it there first (systemctl stop keepalived), so it stops claiming an address it no longer has.

With every node removed, the address goes back to Available and stays a Floating IP, ready for new nodes. You can also attach and detach it from a node’s own page; see Attach a Floating IP to a node.