Check if ipv6 protocol support is enabled or disabled (0 – on, 1 – off):
cat /proc/sys/net/ipv6/conf/all/disable_ipv6
To disable it, open the configuration file /etc/sysctl.conf in a text editor and specify:
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
Apply the changes:
sudo sysctl -p
Let’s see if there are ipv6 addresses on the network interfaces:
ifconfig | grep inet6
See also my article:
Lowering the priority of IPv6