3.3.1 filter

The filter table handles normal traffic. It is used to restrict certain types of traffic. This table contains three built-in chains.

• INPUT: this chain applies to packets/fragments that has the local host as their destinations.
• OUTPUT: this chain applies to packets/fragments originated from the local host.
• FORWARD: this chain applies to packets/fragments that are routed through the local host. This means neither the source nor destination of these packets should match the local host.