18.3. Options Used within iptables Commands
Rules for filtering packets are put in place using the iptables command. The following aspects of the packet are most often used as criteria:
Packet Type — Specifies the type of packets the command filters.
Packet Source/Destination — Specifies which packets the command filters based on the source or destination of the packet.
Target — Specifies what action is taken on packets matching the above criteria.
For more information on specific options which address these aspects of a packet, refer to Section 18.3.4, “iptables Match Options” and Section 18.3.5, “Target Options”.
The options used with given iptables rules must be grouped logically, based on the purpose and conditions of the overall rule, for the rule to be valid. The remainder of this section explains commonly-used options for the iptables command.