How to Enable IPv6 in Ubuntu

IPv6 is a modern Internet Protocol with more features than the popular IPv4 protocol. Compared to IPv4, IPv6 uses 128-bit IP address so there is less private address collision, better quality to better flow control and faster authentication. It has a simple header format and efficient routing making it much faster than IPv4. But by default, it is disabled in Linux. In this article, we will learn how to enable IPv6 in Ubuntu.

How to Enable IPv6 in Ubuntu

Here are the steps to enable IPv6 in Ubuntu.

1. Edit sysctl.conf file

First of all, log into Ubuntu terminal as admin with root access. Then run the following command to open sysctl.conf file in vi editor.

$ vi /etc/sysctl.conf

Then add the following lines to your file.

net.ipv6.conf.default.disable_ipv6 = 0
net.ipv6.conf.all.disable_ipv6 = 0

Save and close the file.

2. Editing Interfaces File

Next, make a backup of /etc/network/interfaces file.

$ sudo mv /etc/network/interfaces /etc/network/interfaces-backup

Then open this file in text editor.

$ sudo vi /etc/network/interfaces

Add the following lines to it. Replace IPv7-IP-Address and IPv6-IP-Gateway-Address with Ubuntu IPv6 addresses that have been given to you.

iface eth0 inet6 static
pre-up modprobe ipv6
address IPv6-IP-Address
netmask 64
gateway IPv6-IP-Gateway-Address

3. Restart Network Service

Next restart networking service to apply the changes.

$ service networking restart

4. Verify IPv6 Setup

Finally, run the following command to verify that IPv6 has been enabled in your system.

$ ifconfig eth0

You will see multiple lines of information along with a line starting with inet6… which indicates that Ubuntu is showing IPv6 address.

...
inet6 addr: ...
...

How to Disable IPv6 in Ubuntu

Here are the steps to disable IPv6 in Ubuntu.

1. Verify IPv6 in Ubuntu

First step is to check if IPv6 is enabled in Ubuntu using the following command.

ip a

In the above command, if IPv6 is enabled then will show you a line starting with inet6.

...
inet6
...

2. Using sysctl command

Next, use the following sysctl commands to disable IPv6 in Ubuntu.

$ sudo sysctl -w net.ipv6.conf.all.disable_ipv6=1
$ sudo sysctl -w net.ipv6.conf.default.disable_ipv6=1
$ sudo sysctl -w net.ipv6.conf.lo.disable_ipv6=1

3. Verify Process of Disabling IPv6

Once again, we will run ‘ip a’ command to ensure it is disabled correctly.

$ ip a

This time you will not see a line starting with inet6…

4. Persistently Disable IPv6

The above changes last only till the next system reboot. To make the changes persistent, you need to modify sysctl.conf file.

$ vi /etc/sysctl.conf

Then add the following lines to this file.

net.ipv6.conf.all.disable_ipv6=1
net.ipv6.conf.default.disable_ipv6=1
net.ipv6.conf.lo.disable_ipv6=1

Save and close the file. Run the following command to apply changes.

$ sudo sysctl -p

Run ‘ip a’ command. If you still see inet6 in the output, create the file /etc/rc.local

vi /etc/rc.local

and add the following lines to it.

#!/bin/bash
# /etc/rc.local
/etc/sysctl.d
/etc/init.d/procps restart

exit 0

Use chmod command to make the file executable.

$ sudo chmod 755 /etc/rc.local

The above command will ensure that the file is read at boot time. In this article, we have learnt how to enable IPv6 in Ubuntu.

How to Enable IPv6 in Ubuntu