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' Run the following command to update the grub2 configuration: # update-grub