Firewall fundamentals

The fundamental purpose of a firewall is to establish a barrier between trusted internal networks and untrusted external networks. We may sometimes also refer to personal firewalls, which are firewalls placed on individual nodes, primarily to filter outgoing traffic. All networking firewalls have the ability to perform packet filtering, which is the ability to inspect packets and determine if they conform to the packet filter's filtering rules. If they do not match the rules, the packets will be dropped.

pfSense includes the following explicit rules:

  • On the WAN interface, all RFC 1918 networks (private networks) and bogon networks (those not assigned by the IANA) are blocked.
  • On the LAN interface, there are two

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