Configuring a failover IP

Find out how to add failover IP addresses to your instance's configuration

Last updated 14th April 2021

Objective

You may need to configure failover IP addresses on your instances, for example if you are hosting multiple websites or international services. OVHcloud failover IPs allow you to associate multiple IP addresses with a single network interface.

This guide explains how to add failover IP addresses to your network configuration.

OVHcloud is providing you with services for which you are responsible, with regard to their configuration and management. You are therefore responsible for ensuring they function correctly.

This guide is designed to assist you in common tasks as much as possible. Nevertheless, we recommend that you contact a specialist service provider if you have difficulties or doubts concerning the administration, usage or implementation of services on a server.

Requirements

  • a Public Cloud instance in your OVHcloud account
  • a failover IP address or a failover IP block
  • administrative access (root) via SSH or GUI to your instance
  • basic networking and administration knowledge

Instructions

The following sections contain the configurations for the most commonly used distributions/operating systems. The first step is always to log in to your instance via SSH or a GUI login session (RDP for a Windows instance). The examples below presume you are logged in as a user with elevated permissions (Administrator/sudo).

Concerning different distribution releases, please note that the proper procedure to configure your network interface as well as the file names may have been subject to change. We recommend to consult the manuals and knowledge resources of the respective OS versions if you experience any issues.

Please take note of the following terminology that will be used in code examples and instructions of the guide sections below:

Term Description Examples
IP_FAILOVER A failover IP address assigned to your service 169.254.10.254
NETWORK_INTERFACE The name of the network interface eth0, ens3
ID ID of the IP alias, starting with 0 (depending on the number of additional IPs there are to configure) 0, 1

Debian 10

Step 1: Disable automatic network configuration

Open the following file path with a text editor:

sudo nano /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg

Enter the following line, then save and exit the editor.

network: {config: disabled}

Creating this configuration file will prevent changes to your network configuration from being made automatically.

Step 2: Edit the network configuration file

You can verify your network interface name with this command:

ip a

Open the network configuration file for editing with the following command:

sudo nano /etc/network/interfaces.d/50-cloud-init

Then add the following lines:

auto NETWORK_INTERFACE:ID
iface NETWORK_INTERFACE:ID inet static
address IP_FAILOVER
netmask 255.255.255.255

Step 3: Restart the interface

Apply the changes with the following command:

sudo systemctl restart networking

Ubuntu 20.04

The configuration file for your failover IP addresses is located in /etc/netplan/. In this example it is called "50-cloud-init.yaml". Before making changes, verify the actual file name in this folder. Each failover IP address will need its own line within the file.

Step 1: Disable automatic network configuration

Open the following file path with a text editor:

sudo nano /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg

Enter the following line, then save and exit the editor.

network: {config: disabled}

Creating this configuration file will prevent changes to your network configuration from being made automatically.

Step 2: Edit the configuration file

You can verify your network interface name with this command:

ip a

Open the network configuration file for editing with the following command:

sudo nano /etc/netplan/50-cloud-init.yaml

Do not change the existing lines in the file; add your failover IP address according to the example below:

network:
    version: 2
    ethernets:
        NETWORK_INTERFACE:
            dhcp4: true
            match:
                macaddress: fa:xx:xx:xx:xx:63
            set-name: NETWORK_INTERFACE
            addresses:
            - IP_FAILOVER/32

It is important to respect the alignment of each element in this file as represented in the example above. Do not use the tab key to create your spacing.

Save and close the file.

Step 3: Apply the new network configuration

You can test your configuration using this command:

sudo netplan try

If it is correct, apply it using the following command:

sudo netplan apply

Repeat this procedure for each failover IP address.

Windows Server 2016

Step 1: Verify the network configuration

Right-click on the Start Menu button and open Run.

Type cmd and click OK to open the command line application.

cmdprompt

In order to retrieve the current IP configuration, enter ipconfig at the command prompt.

check main IP configuration

Step 2: Change the IPv4 Properties

Now you need to change the IP properties to a static configuration.

Open the adapter settings in the Windows control panel and then open the Properties of Internet Protocol Version 4 (TCP/IPv4).

change the ip configuration

In the IPv4 Properties window, select Use the following IP address. Enter the IP address which you have retrieved in the first step, then click on Advanced.

Step 3: Add the failover IP in the "Advanced TCP/IP Settings"

In the new window, click on Add... under "IP addresses". Enter your failover IP address and the subnet mask (255.255.255.255).

advance configuration section

Confirm by clicking on Add.

IP fail over configuration

Step 4: Restart the network interface

Back in the control panel (Network Connections), right-click on your network interface and then select Disable.

disabling network

To restart it, right-click on it again and then select Enable.

enabling network

Step 5: Check the new network configuration

Open the command prompt (cmd) and enter ipconfig. The configuration should now include the new failover IP address.

check current network configuration

cPanel (CentOS 7) / Red Hat derivatives

Step 1: Edit the network configuration file

You can verify your network interface name with this command:

ip a

Open the network configuration file for editing:

sudo nano /etc/sysconfig/network-scripts/ifcfg-NETWORK_INTERFACE:ID

Then add these lines:

DEVICE=NETWORK_INTERFACE:ID
BOOTPROTO=static
IPADDR=IP_FAILOVER
NETMASK=255.255.255.255
BROADCAST=IP_FAILOVER
ONBOOT=yes

Step 2: Restart the interface

Apply the changes with the following command:

sudo systemctl restart networking

Plesk

Step 1: Access the Plesk IP management section

In the Plesk control panel, choose Tools & Settings from the left-hand sidebar.

acces to the ip addresses management

Click on IP Addresses under Tools & Resources.

Step 2: Add the additional IP information

In this section, click on the button Add IP Address.

add ip information

Enter your failover IP in the form xxx.xxx.xxx.xxx/32 into the field "IP address and subnet mask", then click on OK.

add ip information

Step 3: Check the current IP configuration

Back in the section "IP Addresses", verify that the failover IP address was added correctly.

current IP configuration

Troubleshooting

First, soft-reboot your instance via the instance's OS or from the OVHcloud Control Panel. If you are still unable to establish a connection from the public network to your failover IP and suspect a network problem, you need to reboot the instance in rescue mode. Then you can set up the failover IP address directly on the instance.

Once you are connected in rescue mode via SSH, enter the following command:

ifconfig ens3:0 IP_FAILOVER netmask 255.255.255.255 broadcast IP_FAILOVER up

To test the connection, simply ping your failover IP from the outside. If it responds in rescue mode, that probably means that there is a configuration error. If, however, the IP is still not working, please inform our support teams by creating a support request in your OVHcloud Control Panel for further investigations.

Go further

Importing a failover IP

Migrating a failover IP

Join our community of users on https://community.ovh.com/en/.


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