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Floating IP

A Floating IP is a public IP address that can quickly move from one server to another. If one server goes down, the Floating IP can switch to a backup server, so your service stays online without interruption.

Example:​

Imagine you have two nodes: Node A and Node B.

  • You attach the same Floating IP to both.
  • You set Node A as the master node with high priority.
  • Node B is the backup node with lower priority.

By default, the Floating IP points to Node A.

But if Node A fails for any reason, the Floating IP will automatically switch to Node B. This happens without any downtime.

Why use it?​

This setup helps keep your services always available, even if one node goes down. It adds failover support and improves network reliability.

How to create a Floating IP and attach to Node?​

  1. Reserve a Floating IP and attach to the node. For more details click here

Commands to configure Floating IP​

Below are the commands to set up a Floating IP on your Ubuntu Node using Keepalived. Users can use other tools as well.

#connect to the Node
ssh root@<node_ip>

sudo apt update

#install keepalived
sudo apt install keepalived -y

Now create a config file for keepalived

cd /etc/keepalived/
touch keepalived.conf
sudo vi keepalived.conf

Now for Master Node edit the keepalived.conf file to set up the Floating IP. Here is an example configuration:

vrrp_instance VI_1 {
    state MASTER
    interface ens3                   # Replace with your network interface
    virtual_router_id 51
    priority 100                     # Higher priority means this node is preferred
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        <Floating_IP>
    }
}

For Backup Nodes , Edit the keepalived.conf file to set up the Floating IP. Here is an example configuration:

vrrp_instance VI_1 {
    state BACKUP
    interface ens3                  # Replace with your network interface
    virtual_router_id 51
    priority 90                    # Lower priority than MASTER
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        <Floating_IP>
    }
}

Now Enable and Start the keepalived

sudo systemctl enable keepalived
sudo systemctl start keepalived
sudo systemctl status keepalived

Verify the Floating IP​

ip addr show ens3 | grep <Floating_IP>