How to Set Up a Firewall with iptables on Ubuntu and CentOS

In this tutorial, we are going to show you how to set up a firewall with iptables on a Linux VPS running Ubuntu or CentOS as an operating system. Iptables is an administration tool for IPv4 packet filtering and NAT and it is used to set up and manage the tables of IPv4 packet filter rules in the Linux kernel. Properly configuring and setting up a firewall is one of the most important and crucial things you need to do to secure your server.