Configure IP Aliasing on a Dedicated Server

Add and configure Additional IP addresses on your OVHcloud dedicated server for multi-site or service hosting

Info

This article is about Additional IPv4 configuration on a public interface. You can also configure Primary IPv6 addresses on your dedicated servers using this guide.

Additional IP addresses can also be configured in a vRack (private network), which allows interconnection over a wide range of OVHcloud services, offering more flexibility.

Learn how to configure Additional IP addresses in a vRack with our guides for IPv4 and IPv6.

Objective

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

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

Warning

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 dedicated server in your OVHcloud account
An Additional IP address or an Additional IP block (RIPE or ARIN)
Access via SSH or remote desktop connection for Windows
Basic networking and administration knowledge

Warning

This feature might be unavailable or limited on servers of the Eco product line.

Please visit our comparison page for more information.

Instructions

The following sections cover the distributions we currently offer and the most commonly used operating systems. The first step is always to log in to your server via SSH or a GUI login session (RDP for a Windows server).

Info

Concerning different distribution releases, the procedure for configuring your network interface and file names may have changed. We recommend consulting 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
ADDITIONAL_IP	An Additional IP address assigned to your service	203.0.113.1
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

In the examples below, we use the nano text editor. If it isn't installed on your OS, you will be prompted to install it, but you can use any text editor you prefer.

Tip

Select the tab corresponding to your operating system.

Fedora 43+ / AlmaLinux (10) / Rocky Linux (10)

Debian 12+ and Ubuntu 20.04+

AlmaLinux / Rocky Linux

cPanel

Windows Servers

Plesk

Fedora 43 and following, AlmaLinux & Rocky Linux (10)

Fedora now uses keyfiles. NetworkManager previously stored network profiles in ifcfg format in this directory: /etc/sysconfig/network-scripts/. However, the ifcfg format is now deprecated. By default, NetworkManager no longer creates new profiles in this format. The configuration file is now found in /etc/NetworkManager/system-connections/.

Step 1: Create a backup

Info

Note that the name of the network file in our example may differ from your own. Please adjust to your appropriate name.

First, make a copy of the configuration file, so that you can revert at any time. In our example, our configuration file is called cloud-init-eno1.nmconnection.

sudo cp -r /etc/NetworkManager/system-connections/cloud-init-eno1.nmconnection /etc/NetworkManager/system-connections/cloud-init-eno1.nmconnection.bak

Step 2: Edit the config file

Info

Please note that the name of the network file in our example may differ from yours. Please adapt the commands to your file name.

Run one of the following commands to find the name of your network interface before editing the appropriate network file:

ip a

nmcli connection show

Do not modify the existing lines in the configuration file, add your Additional IP to the file as follows, replacing ADDITIONAL_IP/32 with your own values:

sudo nano /etc/NetworkManager/system-connections/cloud-init-eno1.nmconnection

[ipv4]
method=auto
may-fail=false
address1=ADDITIONAL_IP/32

If you have two Additional IPs to configure, the configuration should look like this:

[ipv4]
method=auto
may-fail=false
address1=ADDITIONAL_IP1/32
address2=ADDITIONAL_IP2/32

Configuration example

[ipv4]
method=auto
may-fail=false
address1=203.0.113.1/32

Step 3: Restart the interface

You now need to restart your interface:

sudo systemctl restart NetworkManager

Debian 12, Ubuntu 20.04 and following

By default, the configuration files are located in the /etc/netplan directory.

The best practice approach is to create a separate configuration file to set up Additional IP addresses. This way, you can easily revert the changes in case of an error.

Step 1: Determine the interface

ip a

Note the name of the interface (the one on which your server's main IP address is configured).

Step 2: Create and edit the configuration file

Next, create a configuration file with a .yaml extension. In our example, our file is called 51-cloud-init.yaml.

sudo nano /etc/netplan/51-cloud-init.yaml

Edit the file with the content below, replacing INTERFACE_NAME and ADDITIONAL_IP with your own values:

network:
   version: 2
   ethernets:
       INTERFACE_NAME:
           dhcp4: true
           addresses:
           - ADDITIONAL_IP/32

If you have two Additional IPs to configure, the configuration file should look like this:

network:
   version: 2
   ethernets:
       INTERFACE_NAME:
           dhcp4: true
           addresses:
           - ADDITIONAL_IP1/32
           - ADDITIONAL_IP2/32

Warning

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. Only the space key is needed.

Configuration example

network:
   version: 2
   ethernets:
       eth0:
           dhcp4: true
           addresses:
           - 203.0.113.1/32

Save and close the file, then test the configuration with the following command:

sudo netplan try

Step 3: Apply the change

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

sudo netplan apply

Info

When using the netplan try command, it is possible that the system returns a warning message such as Permissions for /etc/netplan/xx-cloud-init.yaml are too open. Netplan configuration should NOT be accessible by others. This simply means that the file does not have restrictive permissions. This does not affect the configuration of your Additional IP. For more information about file permissions, consult the official documentation of ubuntu.

AlmaLinux (8/9) & Rocky Linux (8/9)

The main configuration file is located in /etc/sysconfig/network-scripts/. In this example it is called ifcfg-eth0. Before making changes, verify the actual file name in this folder.

For each Additional IP to be configured, create a separate configuration file with the following parameters: ifcfg-NETWORK_INTERFACE:ID. Where NETWORK_INTERFACE is the physical interface and ID is the virtual network interface or ethernet alias starting with a value of 0. For example, for our interface named eth0 the first alias is eth0:0, the second alias is eth0:1, etc.

Step 1: Determine the interface

ip a

Note the name of the interface (the one on which your server's main IP address is configured).

Step 2: Create the configuration file

First, create the configuration file. Replace NETWORK_INTERFACE:ID with your own values.

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

Next, edit the file with the content below, replacing NETWORK_INTERFACE:ID, and ADDITIONAL_IP with your own values:

DEVICE=NETWORK_INTERFACE:ID
ONBOOT=yes
BOOTPROTO=none # For CentOS use "static"
IPADDR=ADDITIONAL_IP
NETMASK=255.255.255.255
BROADCAST=ADDITIONAL_IP

Configuration example

DEVICE=eth0:0
ONBOOT=yes
BOOTPROTO=none # For CentOS use "static"
IPADDR=203.0.113.1
NETMASK=255.255.255.255
BROADCAST=203.0.113.1

Step 3: Restart the interface

Next, restart the network interface with the following command:

sudo systemctl restart NetworkManager

cPanel

Step 1: Access the WHM IP management section

In the WHM control panel, click on IP Functions and select Add a New IP Address in the left-hand sidebar.

Step 2: Add the Additional IP information

Enter your Additional IP in the form xxx.xxx.xxx.xxx into the field "New IP or IP range to add".

Select 255.255.255.255 as your subnet mask, then click on Submit.

Warning

Please note that if you have more than one IP to configure on the same block and you add them all at once, the WHM system will force you to use the subnet mask 255.255.255.0. We do not recommend using this configuration. Instead, you need to add each IP individually in order to use the proper subnet mask 255.255.255.255.

Step 3: Check the current IP configuration

Back in the section IP Functions, click on Show or Delete Current IP Addresses to verify that the Additional IP address was added correctly.

Windows Servers

Windows servers are often DHCP-enabled in the network configuration. If you have already set up an Additional IP or switched your configuration to a fixed IP, go directly to the next step.

Otherwise, first switch from a network-level DHCP configuration to a fixed IP configuration.

Open the command prompt cmd or powershell, then type the following command:

ipconfig

This will return a result similar to the following example:

Identify and write down your IPv4, subnet mask, default gateway and the name of the network interface controller (network adapter).

In our example, the server IP is 192.0.2.28.

You can perform the next steps via either a command-line interface or the graphical user interface.

Via a command-line interface (recommended)

In the commands below, replace:

Placeholder	Value
NETWORK_ADAPTER	Name of the network adapter (in our example: Ethernet 2)
IP_ADDRESS	Server IP address (in our example: 192.0.2.28)
SUBNET_MASK	Subnet mask (in our example: 255.255.255.0)
GATEWAY	Default gateway (in our example: 192.0.2.254)
ADDITIONAL_IP	Address of Additional IP you want to add (in our example 203.0.113.1)

Warning

Be careful – the server will no longer be accessible if you enter incorrect information. You will then have to make the corrections in Winrescue mode or via the IPMI.

In the command prompt:

1. Switch to a fixed IP

netsh interface ipv4 set address name="NETWORK_ADAPTER" static IP_ADDRESS SUBNET_MASK GATEWAY

2. Set the DNS server

netsh interface ipv4 set dns name="NETWORK_ADAPTER" static 213.186.33.99

3. Add an Additional IP

netsh interface ipv4 add address "NETWORK_ADAPTER" ADDITIONAL_IP 255.255.255.255

Your Additional IP is now functional.

Via the graphical user interface

Go to Start > Control Panel > Network and Internet > Network and Sharing Centre > Change Adapter Settings (in the left-hand menu).
Right-click on your network connection, in our example Ethernet 2.
Click on Properties.
Select Internet Protocol Version 4 (TCP/IPv4), then click on Properties.
Click on Use the following IP address and type in your server's primary IP, subnet mask and default gateway information obtained by using the ipconfig command above. In the "Preferred DNS Server" box, type 213.186.33.99.

TCP/IPv4 Properties with primary IP address and DNS configured

Warning

Be careful – the server will no longer be accessible if you enter incorrect information. You will then have to make the corrections in Winrescue mode or via the IPMI.

Then click on Advanced (still in the TCP/IP Settings).

TCP/IPv4 Properties with Advanced button highlighted

In the IP Address section, click Add:

Type in your Additional IP and the subnet mask 255.255.255.255. Then click on Add

Click on OK to apply your configuration.

Your Additional IP is now functional, you can verify the configuration with the following command:

ipconfig

This will return a result similar to the following example:

Plesk

Step 1: Access the Plesk IP management section

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

Click on IP Addresses under Tools & Resources.

Step 2: Add the Additional IP information

In this section, click Add IP Address.

Plesk Add IP Address button in the IP management section

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

Plesk form with Additional IP and subnet mask fields

Step 3: Check the current IP configuration

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

Troubleshooting

If restarting the interface does not work, reboot your server from the command line or its GUI. If you are still unable to establish a connection from the public network to your Additional IP and suspect a network problem, you need to reboot the server in rescue mode. Then you can set up the Additional IP address directly on the server.

Once you are connected to your server via SSH, enter the following command:

ifconfig eth0:0 ADDITIONAL_IP netmask 255.255.255.255 broadcast ADDITIONAL_IP up

To test the connection, ping your Additional IP from outside. If it responds in rescue mode, this indicates a configuration error. If, however, the IP is still not working, please open a ticket with the support team via the OVHcloud Help Center with the following information:

The operating system name and version you are using on your server.
The name and directory of the network configuration file.
The content of that file.

Go further

Configuring a network bridge

Moving an Additional IP on a Dedicated Server

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