OUTPUT – The OUTPUT chain is used to manage outgoing packets and connections.

You’re unlikely to use this chain unless you’re routing or looking for forwarding specifically.

FORWARD – The FORWARD chain filters incoming packets that are being forwarded to a different end location.

You can do this based on port, protocol, and source IP address. Here you can block or allow new connections. INPUT – The INPUT chain is the rule that controls incoming packets.The filter’s tables have three chains you’ll encounter on IPTables INPUT, FORWARD and OUTPUT. One of the fundamental concepts to come to grips with in IPTables is that of chains. If you already have these then it is time to begin. Before we get to the heart of IPTables you need to make sure that you have a VPA running Ubuntu 16.04 and a local machine with an SSH client. In this article, we’re going to provide you with a basic guide to IPTables and introduce you to the fundamentals.

Entering the wrong command can lock you out of IPTables altogether until you address the problem within the physical machine.

That being said, you need to be very careful when making changes to IPTables rules. There are a range of core commands that act as your bread and butter for controlling traffic. While users who are new to command line interfaces find there is a learning curve attached to IPTables, the utility itself is simple enough to use. If you’re new to IPTables then one of the first things you need to do is update it or install it is using the following command: $ sudo apt-get install iptables Administrators often use the IPTables firewall to allow or block traffic into their networks. This program is mainly available as a default utility on Ubuntu. IPTables is the name of a firewall system that operates through the command line on Linux.

Iptables chains