Disabling IPv6 on Linux

First, check whether IPv6 protocol support is enabled or disabled (0 – on, 1 – off):

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

To temporarily disable, run the following commands:

sudo sysctl net.ipv6.conf.all.disable_ipv6=1
sudo sysctl net.ipv6.conf.default.disable_ipv6=1

Here is an example of disabling IPv6 on a specific interface:

sudo sysctl net.ipv6.conf.lo.disable_ipv6=1
sudo sysctl net.ipv6.conf.eth0.disable_ipv6=1

To keep IPv6 disabled after a server restart, open the /etc/sysctl.conf configuration file in a text editor and enter:

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

Apply the changes:

sudo sysctl -p

Let’s see if there are ipv6 addresses on the network interfaces:

ifconfig | grep inet6
ip addr show | grep net6

See also my article:
Lowering the priority of IPv6

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