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Configuring IPv6 on a VPS

Find out how to configure IPv6 on your OVHcloud VPS

Last updated 18th January 2021

Objective

IPv6 is the latest version of the Internet Protocol. Each OVHcloud VPS server is delivered with an IPv4 address and an IPv6 address. However, only IPv4 is configured by default. If you need to configure IPv6, it has to be set up manually on your system.

This guide explains how to configure IPv6 on your OVHcloud VPS using various methods.

OVHcloud is providing you with services for which you are responsible, with regard to their configuration and security. Since we have no administrative access to your devices, it is your responsibility to manage the software and to ensure they function correctly.

This guide is designed to assist you in common tasks as much as possible. Nevertheless, we recommend contacting a specialised provider and/or the software publisher for the service if you encounter any difficulties. We will not be able to assist you ourselves. You can find more information in the “Go further” section of this guide.

Requirements

Instructions

Configuring IPv6 on your VPS is done in multiple steps. At several points in the process you will be prompted to enter commands or to customise configuration files of your server.

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

Term Description Example
YOUR_IPV6 The IPv6 address assigned to your service 2001:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:yyyy
IPv6_PREFIX The prefix (or netmask) of your IPv6 block, usually 128 2001:xxxx:xxxx:xxxx::/128
IPv6_GATEWAY The gateway of your IPv6 block 2001:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:zzzz

Step 1: Retrieve the necessary network information

The first step is to identify the IPv6 address and the IPv6 gateway assigned to your server. There are two ways of doing this:

Via the OVHcloud Control Panel

Log in to the OVHcloud Control Panel, and open the Bare Metal Cloud section. Click Virtual Private Servers in the services bar on the left-hand side, then choose the VPS server concerned.

The IPv6 address and the IPv6 gateway assigned to your server will appear in the IP section of the Home tab. Once you have copied them, continue with applying the IPv6 configuration.

configureipv6

Via the OVHcloud API

On the OVHcloud API page click on Login in the top-right corner. On the following page, enter the credentials of your OVHcloud account.

Use this call to retrieve the IPv6 address assigned to your server:

The following call allows you to recover the IPv6 gateway assigned to your server:

Once you have retrieved these addresses, continue with applying the IPv6 configuration.

Step 2: Apply the IPv6 configuration

Once you have gathered the necessary information for the IPv6 configuration, log in to your VPS via SSH. If you require assistance, please refer to this guide: Introduction to SSH.

There are several ways to apply the IPv6 configuration. Use whichever method best suits your situation and requirements:

Non-persistent application

This configuration will be lost after a restart of your VPS (non-persistent configuration).

Connect to your server via SSH and enter the following commands. Take care to tailor these with:

  • the network information, retrieved in the previous step (YOUR_IPV6, IPV6_PREFIX and IPV6_GATEWAY)
  • the network interface (if your server is not using eth0)
ip addr add YOUR_IPV6/IPV6_PREFIX dev eth0
ip -6 route add IPV6_GATEWAY dev eth0
ip -6 route add default via IPV6_GATEWAY dev eth0

Persistent application on Debian and its derivatives (Ubuntu, Crunchbang, SteamOS, etc.)

Before modifying a configuration file, always create a backup of the original.

There are two ways to configure your network depending on the operating system installed on your server:

In some cases (such as Debian 9), the appropriate method may not be the one specified above. To make sure, browse your system to check which one is active. Visit https://netplan.io/ for more information, if necessary.
Moreover, keep in mind that the exact file names may vary.

Configuration of interfaces files

The best practice approach is to create a configuration file in the directory /etc/network/interfaces.d/:

nano /etc/network/interfaces.d/51-cloud-init-ipv6.cfg

This allows you to separate the IPv6 configuration and easily revert the changes in case of an error.

Add the following lines to the file. Replace the generic elements (i.e. YOUR_IPV6, IPV6_PREFIX and IPV6_GATEWAY) as well as the network interface (if your server is not using eth0) with your specific values.

auto eth0
iface eth0 inet6 static
mtu 1500
address YOUR_IPV6
netmask IPV6_PREFIX
post-up /sbin/ip -6 route add IPV6_GATEWAY dev eth0
post-up /sbin/ip -6 route add default via IPV6_GATEWAY dev eth0
pre-down /sbin/ip -6 route del default via IPV6_GATEWAY dev eth0
pre-down /sbin/ip -6 route del IPV6_GATEWAY dev eth0

Then restart your network service with one of the following commands:

service networking restart
systemctl restart networking

Alternatively, you can add the configuration above to one of the following files (with sudo privileges), depending on the generation of the operating system installed on the server:

  • the /etc/network/interfaces file
  • the /etc/network/interfaces.d/50-cloud-init.cfg file

We recommend that you back up up the relevant configuration file. For example, use the following command:

cp /etc/network/interfaces /etc/network/interfaces.back

You will then be able to revert the changes, using the commands below:

rm -f /etc/network/interfaces
cp /etc/network/interfaces.back /etc/network/interfaces
Configuration using Netplan

The network configuration files are located in the /etc/netplan/ directory. We recommend that you start by backing up the relevant configuration file. In this case, copy the 50-cloud-init.yaml file using the following commands:

cd /etc/netplan/
mkdir backup
cp 50-cloud-init.yaml backup/50-cloud-init.yaml

You will then be able to revert the changes, using the commands below:

rm -f /etc/netplan/50-cloud-init.yaml
cp /etc/netplan/backup/50-cloud-init.yaml /etc/netplan/50-cloud-init.yaml

Before editing it, create a copy of the IPv6 configuration file:

cd /etc/netplan
cp 50-cloud-init.yaml 51-cloud-init-ipv6.yaml

Then edit the 51-cloud-init-ipv6.yaml file, adding the IPv6 configuration of your server. Replace the generic elements (i.e. YOUR_IPV6, IPV6_PREFIX and IPV6_GATEWAY) as well as the network interface (if your server is not using eth0) with your specific values.

network:
    version: 2
    ethernets:
        eth0:
            dhcp6: no
            match:
              name: eth0
            addresses:
              - "YOUR_IPV6/IPv6_PREFIX"
            gateway6: "IPv6_GATEWAY"
            routes:
              - to: "IPv6_GATEWAY"
                scope: link

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.

You can test your configuration using this command:

netplan try

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

netplan apply

Persistent application on Red Hat and its derivatives (CentOS, ClearOS, etc.)

The network configuration files are located in the /etc/sysconfig/network-scripts/ directory. We recommend that you start by backing up the relevant configuration file. For example, copy the ifcfg-eth0 file using the following commands. Remember to replace eth0 with your actual interface if necessary.

cd /etc/sysconfig/network-scripts/
mkdir backup
cp ifcfg-eth0 backup/ifcfg-eth0

You will then be able to revert the changes, using the commands below:

rm -f /etc/sysconfig/network-scripts/ifcfg-eth0
cp /etc/sysconfig/network-scripts/backup/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0

Then edit the ifcfg-eth0 file, adding the IPv6 configuration of your server. Replace the generic elements (i.e. YOUR_IPV6, IPV6_PREFIX and IPV6_GATEWAY) with your specific values.

IPV6INIT=yes
IPV6ADDR=YOUR_IPV6/IPV6_PREFIX
IPV6_DEFAULTGW=IPV6_GATEWAY

On CentOS 7, you have to create a routing file in addition to the steps above:

  • Create a file (with sudo privileges), indicating the default IPv6 routes:
# touch /etc/sysconfig/network-scripts/route6-eth0
  • Edit the file and add the lines below. Replace the generic elements (IPV6_GATEWAY and eth0 interface, if necessary) with your specific values.
IPV6_GATEWAY dev eth0
default via IPV6_GATEWAY

Finally, restart your network service to allow the system to apply the new configuration with one of the following commands:

service networking restart
systemctl restart networking

Persistent application on Windows Server

By default, IPv6 is not configured on Windows Servers. To enable it, open the Control Panel and click on View network status and tasks, then on Change adapter settings.

configureipv6

Click on Ethernet to open the settings and click on the Properties button to view the Ethernet Properties.

Select Internet Protocol Version 6 (TCP/IPv6), then click on the Properties button.

configureipv6

In the IPv6 Properties window, select Use the following IPv6 address. Enter the IP addresses which you have retrieved in the first step.

You also have the option of entering the IPv6 DNS resolvers of your choice under Use the following DNS server addresses. This is not mandatory if the DNS resolvers of the IPv4 configuration are already functional.

Finally, tick the Validate settings upon exit box and click the OK button to validate your changes. An error message may appear if the specified gateway is not on the same IPv6 subnet (/128 and /64 for example). You can ignore this message and continue to the next step regardless.

configureipv6

Step 3: Verify the configuration and test the connection

To verify that the configuration is functional, there are several possible commands, depending on the operating system.

  • For a GNU/Linux-based system, here are two examples for the eth0 interface (to be adapted if necessary):
ip -6 addr show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
    inet6 2001:xxxx:xxxx:xxxx:xxxx:xxxx:zzzz/128 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::f816:3eff:fec0:c336/64 scope link
       valid_lft forever preferred_lft forever
ifconfig eth0
eth0      Link encap:Ethernet  HWaddr ab:cd:ef:gf:ij:kl
          inet addr:aa.bb.cc.dd  Bcast:aa.bb.cc.ee  Mask:255.255.255.255
          inet6 addr: 2001:xxxx:xxxx:xxxx:xxxx:xxxx:zzzz/128 Scope:Global
          inet6 addr: fe80::f816:3eff:fec0:c336/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          [...]

To test the connection, you can use the following command:

ping6 proof.ovh.net
  • For a Windows-based system, use the following command:
ipconfig

Windows IP Configuration

Ethernet adapter Ethernet:

   Connection-specific DNS Suffix  . : openstacklocal
   IPv6 Address. . . . . . . . . . . : 2001:xxxx:xxxx:xxxx::zzzz
   Link-local IPv6 Address . . . . . : fe80::d928:7a00:5ba6:951b%3
   IPv4 Address. . . . . . . . . . . : 51.xxx.xxx.xxx
   Subnet Mask . . . . . . . . . . . : 255.255.255.255
   Default Gateway . . . . . . . . . : 2001:xxxx:xxxx:xxxx::y
                                       51.xxx.xxx.y

To test the connection, you can use the following command:

ping -6 proof.ovh.net

You can also test the connection to another remote server. However, it is necessary for IPv6 to be active on the remote server for this operation to work.

If, despite these changes, IPv6 does not seem work on your server, it is possible (in rare cases) that you will have to carry out additional modifications. In such cases, try the following steps:

  • Depending on the operating system, try to change the prefix (or netmask) of your IP address from /128 to /64. This will include the IPv6 gateway in your subnet.

  • In addition to restarting the network service, it may be necessary to reboot your server to finalise your IPv6 configuration.

  • In Windows, verify that the firewall allows ICMP requests for IPv6.

Step 4: Disable Cloud-init network management (optional)

This step does not apply to Windows-based systems.

Cloud-init is a package installed by default on a VPS. It functions as a framework to run a script after initially creating your server or rebooting it. The mechanics in place allow the underlying OpenStack infrastructure to inject scripts into the Cloud-init environment and therefore the server configuration.

Depending on the operating system, Cloud-init will manage: the network, the hostname, the resolv.conf file, or the automatic partitioning of the hard disk, in case of an upgrade.

In the case of newer distributions (such as CentOS, Debian 9, Ubuntu 16.x, and later), the default configuration of Cloud-init might sometimes automatically reset the network configuration when the server starts up.

This is relevant for specific use cases in which it is recommended to avoid the reset by disabling automatic network management in Cloud-init. To do this, use the following command to create a file /etc/cloud/cloud.cfg.d/98-disable-network-config.cfg with the value network: {config: disabled}:

echo "network: {config: disabled}" > /etc/cloud/cloud.cfg.d/98-disable-network-config.cfg

It might be necessary to reboot the server for the change to take effect.

In order to return to automatic management of your network by Cloud-init, delete the newly created file or move it to another directory.

Go further

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


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