How to Configure IPv6 on a Linux Dedicated Server

The internet is continuously changing, and the depletion of IPv4 addresses is not far-fetched. IPv6 is not something of the future anymore but a requirement that needs to be considered now. Having a fundamental understanding of IPv6 is essential for future-proofing your infrastructure. It can play a crucial role in decision-making, especially when managing a dedicated Linux server, particularly one running the latest Ubuntu 24 release.

This guide has everything you need to know to configure IPv6 on a Linux dedicated server. At the end of this guide, you will have a working IPv6 solution to the point where you can accept the new era of the internet connection.

#Why IPv6 matters now more than ever

Before going over the technical details, let us understand the importance of IPv6:

• Address Exhaustion: IP addresses (IPv4) are running out, and most of the increasing devices and services are becoming dependent on IPv6.
• Scalability: IPv6 provides a number of addresses that are nearly astronomical, which means that it can connect every device on Earth.
• Efficiency: IPv6 has simplified the process of network configuration through stateless autoconfiguration (SLAAC) and also enhances the routing efficiency.
• Security: IPv6 has been thought out with security in mind, with IPsec being a mandatory component.
• Performance: In multiple cases, IPv6 is superior in performance; its packet headers are less complicated, and the routing paths are more straightforward.

To a dedicated server case, IPv6 will enable your server to connect directly with services and users that exclusively use IPv6, increasing its reach and making it compatible in the long term.

#Prerequisites

Before starting, ensure you have:

• A dedicated Linux server running (I am using Ubuntu 24.04)
• Root or sudo access to the server
• An IPv6 address block assigned by your hosting provider or network administrator
• Basic knowledge of Linux terminal commands and networking concepts

#Configuring IPv6 on a Linux dedicated server

Below are the steps involved in configuring IPv6 on a Linux dedicated server.

#Step 1: Verify IPv6 support

First, check if your server has IPv6 enabled and if the kernel supports it.

cat /proc/sys/net/ipv6/conf/all/disable_ipv6

Output0

• 0 means IPv6 is enabled.
• 1 means IPv6 is disabled.

If the output is 1, enable IPv6 by running:

sudo sysctl -w net.ipv6.conf.all.disable_ipv6=0

#Step 2: Check current network configuration

Verify the network interfaces and their current IPv6 configuration.

ip -6 addr show

Output1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN qlen 1000
    inet6 ::1/128 scope host noprefixroute 
       valid_lft forever preferred_lft forever
2: enp0s1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 fd7d:106f:a73e:8d9c:b310:2e19:39e5:628f/64 scope global temporary dynamic 
       valid_lft 604028sec preferred_lft 85297sec
    inet6 fd7d:106f:a73e:8d9c:8483:b6ff:feae:3a4c/64 scope global dynamic mngtmpaddr 
       valid_lft 2591974sec preferred_lft 604774sec
    inet6 fe80::8483:b6ff:feae:3a4c/64 scope link 
       valid_lft forever preferred_lft forever

• lo is the loopback interface with ::1/128.
• enp0s1 (or your interface name) may show a link-local address (fe80::/64) or/and a Unique Local Address (fd7d::/64). If no global IPv6 address (e.g., 2001:db8::) appears, you need to configure one.

#Step 3: Configure IPv6 address

Ubuntu 24 uses Netplan for network configuration. Netplan configuration files are located in /etc/netplan/.

#Check Existing Netplan Configuration

List the Netplan configuration files:

ls /etc/netplan/

Output50-cloud-init.yaml 01-network-manager-all.yaml

#Backup the Configuration

Always back up the existing configuration:

sudo cp /etc/netplan/01-network-manager-all.yaml /etc/netplan/01-network-manager-all-yaml.backup

#Edit the Netplan Configuration

Open the Netplan file for editing:

sudo nano /etc/netplan/01-network-manager-all.yaml

Add or modify the IPv6 configuration under the appropriate interface. Here’s an example configuration:

network:
  version: 2
  renderer: NetworkManager
  ethernets:
    enp0s1:
      dhcp4: no
      addresses:
        - 192.168.2.107/24
        - 2001:db8:abcd:0012::1/64
      routes:
        - to: default
          via: 192.168.2.1
        - to: default
          via: "2001:db8:abcd:0012::1"

      nameservers:
        addresses:
          - 8.8.8.8
          - 2001:4860:4860::8888

Here, I am configuring the address starting with 2001 to use publicly routable IPv6 addresses. 2001:4860:4860::8888 is the address of Google DNS that your server will use to translate domain names into IP addresses, facilitating outbound connections to other services on the internet.

Below are the details of configuration parameters:

• addresses: Specifies the static IPv6 address and subnet
• nameservers: Lists IPv6 DNS servers
• Save the file (Ctrl+O, Enter, Ctrl+X in nano)

#Step 4: Apply the Netplan configuration

Test and apply the new configuration:

sudo netplan try

OutputDo you want to keep these settings?

Press ENTER before the timeout to accept the new configuration

Changes will revert in 88 seconds

Press Enter to accept. If there are errors, Netplan will revert after 120 seconds, allowing you to fix the configuration.

If the test is successful, apply the configuration permanently:

sudo netplan apply

#Step 5: Verify IPv6 configuration

Check if the IPv6 address is assigned:

ip  -6 addr show

Outputubuntu@ubuntu:~$ ip -6 addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN qlen 1000
    inet6 ::1/128 scope host noprefixroute 
       valid_lft forever preferred_lft forever
2: enp0s1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
    inet6 2001:db8:abcd:12::1/64 scope global 
       valid_lft forever preferred_lft forever

Check the routing table:

ip -6 route

Output2001:db8:abcd:12::/64 dev enp0s1 proto kernel metric 256 pref medium

#Step 6: Test IPv6 connectivity

Test connectivity to an IPv6-enabled server (e.g., Google’s DNS server):

ping6 google.com

OutputPING google.com(2404:6800:4003:c01::8b) 56 data bytes
64 bytes from 2404:6800:4003:c01::8b: icmp_seq=1 ttl=117 time=12.3 ms

#Step 7: Configure the firewall for IPv6

Ubuntu 24 uses UFW (Uncomplicated Firewall) by default. Ensure IPv6 is enabled in UFW.

#Enable IPv6 in UFW

Edit the UFW configuration:

sudo nano /etc/default/ufw

Ensure the IPV6 setting is enabled:

IPV6=yes

Save and exit the file.

#Allow necessary ports

For example, allow SSH (port 22) and HTTP (port 80):

sudo ufw allow proto tcp to any port 22

OutputRules updated
Rules updated (v6)

sudo ufw allow proto tcp to any port 80

OutputRules updated
Rules updated (v6)

Reload UFW:

sudo ufw reload

OutputFirewall reloaded

sudo ufw status

OutputStatus: active

To                         Action      From
--                         ------      ----
22/tcp                     ALLOW       Anywhere                  
80/tcp                     ALLOW       Anywhere                  
22/tcp (v6)                ALLOW       Anywhere (v6)             
80/tcp (v6)                ALLOW       Anywhere (v6)  

#Conclusion

When configuring IPv6 on a dedicated Ubuntu 24 server, the main steps are to verify that a feature is supported in the kernel. Following these instructions, your server would become IPv6-ready and make it work in the new networks. To maintain a healthy configuration, you have to frequently consult documentation about the concrete IPv6 configuration at your hosting provider and fiddle to maintain connectivity.