Information
Although IPv6 has many advantages over IPv4, not all organizations have IPv6 or dual stack configurations implemented.
Rationale:
If IPv6 or dual stack is not to be used, it is recommended that IPv6 be disabled to reduce the attack surface of the system.
Solution
Edit /etc/default/grub and add ipv6.disable=1 to the GRUB_CMDLINE_LINUX parameters:
GRUB_CMDLINE_LINUX='ipv6.disable=1'
Depending or your distribution, run the appropriate following command to update the grub2 configuration:
# grub2-mkconfig -o /boot/grub2/grub.cfg
or
# update-grub