The purpose of this guide is to show some of the most common iptables commands for Linux systems. iptables is the firewall built into all Linux distributions. Even distros like Ubuntu, which utilizes ufw (uncomplicated firewall), and Red Hat, which utilizes firewalld still pass their commands to iptables and use it in the background.
This is a companion discussion topic for the original entry at https://linuxconfig.org/collection-of-basic-linux-firewall-iptables-rules