IPv6

https://test-ipv6.com/

https://ipv6-test.com/

Check your IPv6 configuration

Disable IPv6 on a system

At the end of /etc/sysctl.conf add:

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

sysctl -p

Force reload of the kernel parameters as in /etc/sysctl.conf

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

Check if IPv6 has been disabled, then the file as 1, else 0