How to configure a failover IP on Debian and Ubuntu

You will find below, information on how to configure a failover IP on Dedibox servers running on Debian or Ubuntu Linux.

Failover IP configuration on Debian

1. Connect to your server using SSH.

2. Open the network configuration file /etc/network/interfaces in a text editor, for example nano:

   nano /etc/network/interfaces
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3. Add the failover IP to the configuration as shown in the following example:

   # This file describes the network interfaces available on your system
   # and how to activate them. For more information, see interfaces(5). 
   # The loopback network interface 
   auto lo 
   iface lo inet loopback 
   # The primary network interface 
   auto eth0 
   iface eth0 inet static 
            address 195.154.123.123
            netmask 255.255.255.0 
            gateway 195.154.123.1
   auto eth0:0
   iface eth0:0 inet static
   address ip_failover
   netmask 255.255.255.255
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   Note:

   The interface name eth0 may vary, depending on your OS version and system configuration. Use the ifconfig command to determine the name of your primary network interface.

4. Save the file and exit the editor.

5. Bring up the interface using the following command:

   ifup eth0:0
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Failover IP configuration on Ubuntu

Since the release of version 18.04 (Bionic Beaver) Ubuntu has switched to Netplan for the configuration of network interfaces.

It is a YAML-based configuration system, which simplifies the configuration process.

1. Connect to your Dedibox using SSH.

2. Open the Netplan configuration file of the main interface in a text editor, for example nano:

   sudo nano /etc/netplan/01-netcfg.yaml
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3. Edit the network configuration. The IP addresses have to be written with their CIDR notation. The netmask is /24 for the principal IP of the server and /32 for each failover IP. Your configuration should look as in the following example:

   network:
   version: 2
   renderer: networkd
   ethernets:
       enp1s0f0:
       addresses: [163.172.123.123/24, 212.83.123.123/32]
       gateway4: 163.172.123.1
       nameservers:
           addresses: [ "62.210.16.6", "62.210.16.7" ]
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   Tip:

   Make sure to respect the YAML standards when you edit the file as it might not work if there is a syntax error in your configuration.

4. Activate the new configuration by running the following command:

   sudo netplan apply
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