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What is Iptables?

The traditional Linux firewall tool that filters network packets using configurable chains of rules organized in tables.

Iptables controls network traffic by processing packets through chains of rules in the filter, nat, mangle, and raw tables. The filter table (INPUT, FORWARD, OUTPUT chains) handles packet filtering. The nat table manages Network Address Translation for routing. Rules specify match criteria (source/destination IP, port, protocol) and targets (ACCEPT, DROP, REJECT, LOG). Iptables processes rules sequentially — the first matching rule wins. While being replaced by nftables on modern systems, iptables remains widely used and is the foundation for Docker networking and Kubernetes kube-proxy. The ip6tables variant handles IPv6 traffic.

Related Terms

Network Namespace
A Linux kernel feature that provides isolated network stacks with independent interfaces, routing tables, and firewall rules.
Strace
A diagnostic tool that traces system calls and signals made by a process, useful for debugging and performance analysis.
Daemon
A background process that runs continuously on a system, typically providing services like web serving or logging.
Chroot
A mechanism that changes the apparent root directory for a process and its children, creating an isolated filesystem view.
Nftables
The modern Linux packet filtering framework that replaces iptables with a unified, more efficient rule-processing architecture.
Netstat
A command-line tool that displays network connections, routing tables, and interface statistics on a system.
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