Configuring IP aliasing

Last updated 8th April 2020

Objective

IP aliasing is a special network configuration for your OVHcloud servers, which allows you to associate multiple IP addresses with a single network interface.

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

Requirements

• a Virtual Private Server in your OVHcloud account
• a failover IP address or a failover IP block (RIPE)
• administrative access (root) via SSH or remote desktop (Windows) to your server

Instructions

The following sections contain the configurations for the most commonly used distributions/operating systems.

Debian 9

Step 1: Disable automatic network configuration

First, open the following file, as shown below:

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

Next, edit the file with the configuration shown below. This will prevent changes from being made to your network configuration automatically.

network: {config: disabled}

Step 2: Edit the network configuration file

Next, open the network configuration file for editing with the following command:

# nano /etc/network/interfaces.d/50-cloud-init.cfg

Then edit the file with the following configuration:

auto ens3
iface ens3 inet dhcp

auto ens3:0
iface ens3:0 inet static
address FailoverIP 0
netmask 255.255.255.255

auto ens3:1
iface ens3:1 inet static
address FailoverIP 1
netmask 255.255.255.255

Ubuntu 18.04

Each failover IP address will need its own line within this file. The configuration file for your failover IP addresses should be called "50-cloud-init.yaml".

Step 1: Create the configuration file

Connect to your server via SSH and run the following command:

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

Next, edit the file with the content below:

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

Finally, save and close the file.

Then apply config:

# netplan apply
# netplan try

Repeat this procedure for each failover IP address.

CentOS and Fedora (25 and earlier)

Step 1: Create the source file

First, make a copy of the source file so that you can use it as a template:

cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:0

Step 2: Edit the source file

You can now modify the eth0:0 file in order to replace the IP:

editor /etc/sysconfig/network-scripts/ifcfg-eth0:0

First, replace the name of the device, then replace the existing IP with the failover IP you have received:

DEVICE="eth0:0"
ONBOOT="yes"
BOOTPROTO="none" # For CentOS use "static"
IPADDR="IP_FAILOVER"
NETMASK="255.255.255.255"
BROADCAST="IP_FAILOVER"

Step 3: Restart the interface

You now need to restart your interface:

ifup eth0:0

Windows Server 2012/2016

Step 1: Check the main IP configuration

First of all we need to recover the information of the main IP address:

Step 2: Change the IPv4 Properties

Now we must change the IP properties from 'automatically configuration' to a 'static' configuration manually:

Now we can define the IP information obtained previously:

Step 3: Add the failover IP in the 'Advanced configuration' section

Here we must to define the failover IP information and the correspond netmask (normally the netmask is -> 255.255.255.255)

Step 4: Rebooting the network interface

First we do the disabling process

Then we do the enabling process

Step 5: Checking the new network configuration

Using the console and the ipconfig command we can check the new network configuration

cPanel (on CentOS 6)

Step 1: Create the source file

First, make a copy of the source file, so that you can revert at any time:

cp /etc/ips /etc/ips.bak

Step 2: Edit the source file

You then need to edit the /etc/ips file:

editor /etc/ips

Then add the failover IP to the file:

IP_FAILOVER:255.255.255.255:IP_FAILOVER

Next, add the IP in /etc/ipaddrpool:

IP_FAILOVER

Step 3: Restart the interface

You now need to restart your interface:

/etc/init.d/ipaliases restart

Plesk Onyx 17.x

Step 1: Access to the 'IP Addresses' management inside the control panel:

Access to the Tools & Settings>IP Addresses section:

Step 2: Add the additional IP information:

Click on the Add IP Address button:

Then put the additional IP information in the form and press OK

Step 3: Check the current IP configuration inside Plesk panel:

Troubleshooting

If you are unable to establish a connection from the public network to your alias IP and suspect a network problem, please reboot the server in Rescue Mode and setup the alias directly on the server.

In order to do that, once you have rebooted your server in Rescue Mode, please enter the following command:

ifconfig ens3:0 FAILOVER_IP netmask 255.255.255.255 broadcast FAILOVER_IP up

Replace FAILOVER_IP with the actual IPFO.

Next, simply ping your IPFO from the outside. If it works, it probably means that there is a configuration error that requires to be fixed. If, on the contrary, the IP is still not working, please inform our support team by creating a support request in your OVHcloud Control Panel for further investigations.

Go further

Activating Rescue Mode on VPS

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

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