iptables is the traditional Linux packet filtering command-line interface for Netfilter firewall rules, NAT, packet forwarding, and low-level traffic control. These guides focus on concrete administration tasks such as listing active rules, allowing or blocking traffic, saving rules across reboots, troubleshooting blocked packets, and planning migration from legacy rule sets.
Modern Linux distributions may provide iptables through either legacy or nftables-backed implementations, so each guide should verify the active backend and the runtime result before treating a rule change as complete.