How to safely disable IPv6 on a VPS without removing the interface

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How to disable IPv6 on a VPS server without removing the interface

Often you want to completely disable IPv6, but without removing the interface eth0/ens3/enp1s0 and without breaking cloud providers (Hetzner, Vultr, DigitalOcean, Linode, etc.).

The most reliable and clean method (recommended)

  1. Disable IPv6 on all interfaces via sysctl
sudo sysctl -w net.ipv6.conf.all.disable_ipv6=1
sudo sysctl -w net.ipv6.conf.default.disable_ipv6=1
  1. Make the changes permanent
echo "net.ipv6.conf.all.disable_ipv6 = 1"    | sudo tee -a /etc/sysctl.conf
echo "net.ipv6.conf.default.disable_ipv6 = 1" | sudo tee -a /etc/sysctl.conf

In some distributions it is also better to add:

echo "net.ipv6.conf.lo.disable_ipv6 = 1" | sudo tee -a /etc/sysctl.conf
  1. Apply immediately (without reboot)
sudo sysctl -p

Alternative method — via GRUB (if sysctl did not work)

sudo nano /etc/default/grub

Add/change the line:

GRUB_CMDLINE_LINUX_DEFAULT="quiet ipv6.disable=1"
# or
GRUB_CMDLINE_LINUX="ipv6.disable=1"

Then:

sudo update-grub
sudo reboot

Verification

ip -6 addr          # there should be no global IPv6 addresses
ping6 google.com    # should be "Network is unreachable"
sysctl net.ipv6.conf.all.disable_ipv6   # should return 1

When the sysctl method doesn’t help (very rare)

Add to /etc/sysctl.d/99-disable-ipv6.conf:

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

And reboot.

Good luck!