How to setup firewall

If your Linux server doesn't contain iptables, it is good to install them with command:

sudo apt-get install iptables
sudo apt-get install ip6tables

It is advised to block all ip6tables access:

ip6tables -P INPUT DROP
ip6tables -P OUTPUT DROP
ip6tables -P FORWARD DROP

If you use SSH access to your server, then it is necessary to allow SSH port:

sudo iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
sudo iptables -A INPUT -p tcp --dport ssh -j ACCEPT

Allow communication with node:

• 127.0.0.1 - allowed ip for access to API RPC-JSON

• 16661 - testnet API RPC-JSON port

• 16665 - node communication port

sudo iptables -A INPUT -p tcp -s 127.0.0.1 --dport 16661 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 16661 -j DROP
sudo iptables -A INPUT -p tcp -m tcp --dport 16665 -m state --state NEW,ESTABLISHED -j ACCEPT

At the end, drop all other accesses:

sudo iptables -D INPUT -j DROP
sudo iptables -A INPUT -j DROP

- We recommend installing great Linux utility iptables-permanently which stores your configurations in a file and during boot it restores your configuration automatically.
For installation and store iptables configuration call following command line:

sudo apt-get install iptables-persistent

- Answer YES to all questions.

Recommendation: If you make a change in your configuration uninstall it and install it again to store new configuration.