They can be specified to have multiple matches and on specific targets. The filtering of network traffic is done via the rules. The nat table has two additional chains called PREROUTING and POSTROUTING. Filter has three built-in chains INPUT, OUTPUT, and FORWARD. The default table is filter others are raw, nat, mangle, and security.

Iptables consists of five tables, each for specialized networking jobs. Now, what do iptables consist of? Below the hood, it just contains some tables, chains, and rules. However, it can do all sorts of networking magic you want it to do.

Iptables act as a firewall by blocking incoming network packets from hostile systems. It can inspect, modify, redirect, or drop packets, units of network communications used by our systems. It is a user-space program, with a neat command-line interface that allows users to utilize Netfilter’s raw power in a concise, well-organized manner. The framework is quite low-level and, hence, not feasible for everyday users. It is simply a stack of kernel routines that provide the barebone networking abilities to our system. The Linux kernel contains a framework called Netfilter for networking purposes. Foundation & Structure of Linux IPtables Rules Start honing your networking skills by practicing these iptables rules for a better view of the subject. We have curated this guide carefully and outlined the contents according to that. Fundamental knowledge of the iptables utility and its purpose will make it easier to master the firewall. People often think hard of iptables firewall rules, but in practice, they’re pretty straightforward once you get going.

Iptables examples