iptables

iptables is the traditional Linux firewall tool for configuring packet filtering and NAT rules.

What is iptables?

iptables is a user-space utility for configuring Linux kernel firewall rules, managing packet filtering, network address translation (NAT), and packet mangling.

iptables concepts

Tables (filter, nat, mangle), Chains (INPUT, OUTPUT, FORWARD), Rules, Targets (ACCEPT, DROP, REJECT).

Common misconceptions

"iptables is obsolete" — nftables is successor but iptables still used
"Order doesn't matter" — Rules processed sequentially
"iptables persists automatically" — Need iptables-save/restore