iptables resets when server reboots
Solution 1:
This is the default behavior.
You may want to take a look at the package iptables-persistent to automatically set iptables rules at startup from a configuration file.
Solution 2:
On Ubuntu 16.04:sudo apt-get install iptables-persistent
After that, run next commands every time you want save iptables changes permanently:sudo netfilter-persistent savesudo netfilter-persistent reload