30.3. Firewall Packages

FreeBSD has three firewalls built into the base system: IPFILTER, also known as IPF, IPFIREWALL, also known as IPFW, and PF). FreeBSD also provides two traffic shapers for controlling bandwidth usage: altq(4) and dummynet(4). Dummynet has traditionally been closely tied with IPFW, and ALTQ with PF. Each firewall uses rules to control the access of packets to and from a FreeBSD system, although they go about it in different ways and each has a different rule syntax.

FreeBSD provides multiple firewalls in order to meet the different requirements and preferences for a wide variety of users. Each user should evaluate which firewall best meets their needs.

Since all firewalls are based on inspecting the values of selected packet control fields, the creator of the firewall ruleset must have an understanding of how TCP/IP works, what the different values in the packet control fields are, and how these values are used in a normal session conversation. For a good introduction, refer to Daryl's TCP/IP Primer.

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