Packet Filtering Using Iptables

This document provides an overview of packet filtering using iptables in Linux. It describes what iptables/netfilter are, the tables and chains, packet flow, basic iptables syntax, common targets, and examples of rules for enabling basic services like web, ping, and FTP. The key points are: - Iptables is the userspace tool for configuring the netfilter kernel module that provides firewall and NAT capabilities - Packet filtering is done in the filter table across the INPUT, FORWARD, and OUTPUT chains - Common rules allow establishing connections for web, ping, and handle the multiple connections for FTP - Targets like ACCEPT, DROP, REJECT determine if packets are allowed through the firewall or dropped