How to Disable IPv6 on Linux

IPv6 is the successor to IPv4, designed to address the limitations of the older protocol. But despite its advantages, some systems and applications don’t play nicely with it. If you’re running into network issues or just want to simplify your setup, disabling IPv6 might help.

Here’s a step-by-step guide to disabling IPv6 on most Linux distributions.

Why Disable IPv6?

While IPv6 is the future, here are some reasons you might want to turn it off:

• Some VPNs or firewalls aren’t compatible with IPv6.
• Disabling it can prevent DNS leaks.
• You’re troubleshooting network issues and want to simplify the stack.
• Your network environment only uses IPv4.

Method 1: Temporarily Disable IPv6

This disables IPv6 until the next reboot.

1. Open a terminal.
2. Run the following commands:

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

To confirm it worked:

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

If the output is 1, IPv6 is off.

Method 2: Permanently Disable IPv6

To make the change stick after reboot, you’ll need to edit the system configuration.

For most systems using sysctl.conf:

1. Edit the sysctl config file:

sudo nano /etc/sysctl.conf

2. Add these lines at the bottom:

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

3. Apply the changes:

sudo sysctl -p

For systems using grub (e.g., Ubuntu, Debian):

1. Edit the GRUB config:

sudo nano /etc/default/grub

2. Find the line that starts with GRUB_CMDLINE_LINUX and add the following:

ipv6.disable=1

Example:

GRUB_CMDLINE_LINUX="ipv6.disable=1"

3. Update GRUB:

sudo update-grub

4. Reboot your system:

sudo reboot

How to Check if IPv6 is Disabled

After rebooting, run:

ip a | grep inet6

If no inet6 entries appear, IPv6 is disabled.

Final Notes

Disabling IPv6 should be done with caution, especially if you’re in a mixed environment or using services that require it. Make sure your system and apps don’t rely on it before turning it off.

Got questions or ran into trouble? Drop a comment below — happy to help.