Introduction : Firewall/Packet Filtering on the OnBoard Appliance : Rules

Rules
Each chain can have one or more rules that define the following:
The packet characteristics being filtered. The packet is checked for characteristics defined in the rule, for example, a specific IP header, input and output interfaces and protocol.
What to do when the packet characteristics match the rule. The packet is handled according to the specified action (called a Rule Target, Target Action or Policy).
When a packet is filtered, its characteristics are compared against the rules one-by-one. All characteristics must match.