ip6tables.service is a utility for configuring and maintaining ip6tables ip6tables.service will load the iptables rules saved in the file /etc/sysconfig/ip6tables at boot, otherwise the ip6tables rules will be cleared during a re-boot of the system.
Solution
Run the following commands to unmask, enable and start ip6tables.service : # systemctl unmask ip6tables.service # systemctl --now start ip6tables.service