Iptables Command Line Tool

Internal

• iptables

Overview

iptables always targets the "filter" table by default. In order to change the target table, use the -t <table-name> options.

Commands

List Rules

iptables -L -nv --line-numbers

The command list all rules in the selected chain. If no chain is selected, all chains are listed.

The command applies to the specified table ("filter" is the default). If you need to list rules from a table other than "filter", use -t (example -t nat).

The command is often used with the -n option, in order to avoid long reverse DNS lookups.

Add a Rule to the Default Table

iptables -A <chain> -i <interface> -s <source> -p <protocol> [-m <module> <module-config>] -j <target>

The rule will be added to the "filter" table. If you need to add the rule to a different table, use -t.

The rule will only be added in memory and won't survive a reboot. In order to make the rule permanent TODO.

-A

The chain can be one of INPUT, OUTPUT, FORWARD, PREROUTING and POSTROUTING.

Example of allowing external HTTP access on a specific interface:

iptables -A INPUT -i enp0s25 -p tcp -j ACCEPT