In order to use PF, the PF kernel module must be first loaded. Add the following line to /etc/rc.conf:

Then, run the startup script to load the module:

The PF module will not load if it cannot find the ruleset configuration file. The default location is /etc/pf.conf. If the PF ruleset is located somewhere else, add a line to /etc/rc.conf which specifies the full path to the file:

The sample pf.conf can be found in /usr/share/examples/pf/.

The PF module can also be loaded manually from the command line:

Logging support for PF is provided by pflog.ko which can be loaded by adding the following line to /etc/rc.conf:

Then, run the startup script to load the module:

While it is not necessary to compile PF support into the FreeBSD kernel, some of PF's advanced features are not included in the loadable module, namely pfsync(4), which is a pseudo-device that exposes certain changes to the state table used by PF. It can be paired with carp(4) to create failover firewalls using PF. More information on CARP can be found in of the Handbook.

The following PF kernel options can be found in /usr/src/sys/conf/NOTES:

device pf enables PF support.

device pflog enables the optional pflog(4) pseudo network device which can be used to log traffic to a bpf(4) descriptor. The pflogd(8) daemon can then be used to store the logging information to disk.

device pfsync enables the optional pfsync(4) pseudo-network device that is used to monitor “state changes”.

The following rc.conf(5) statements can be used to configure PF and pflog(4) at boot:

If there is a LAN behind the firewall and packets need to be forwarded for the computers on the LAN, or NAT is required, add the following option:

By default, PF reads its configuration rules from /etc/pf.conf and modifies, drops, or passes packets according to the rules or definitions specified in this file. The FreeBSD installation includes several sample files located in /usr/share/examples/pf/. Refer to the PF FAQ for complete coverage of PF rulesets.

The FreeBSD packet filter mailing list is a good place to ask questions about configuring and running the PF firewall. Do not forget to check the mailing list archives before asking questions.

To control PF, use pfctl(8). Below are some useful options to this command. Review pfctl(8) for a description of all available options:

ALTQ is only available by compiling its support into the FreeBSD kernel. ALTQ is not supported by all network card drivers. Refer to altq(4) for a list of drivers that are supported by the release of FreeBSD.

The following kernel options will enable ALTQ and add additional functionality:

options ALTQ enables the ALTQ framework.

options ALTQ_CBQ enables Class Based Queuing (CBQ). CBQ can be used to divide a connection's bandwidth into different classes or queues to prioritize traffic based on filter rules.

options ALTQ_RED enables Random Early Detection (RED). RED is used to avoid network congestion by measuring the length of the queue and comparing it to the minimum and maximum thresholds for the queue. If the queue is over the maximum, all new packets will be dropped. RED drops packets from different connections randomly.

options ALTQ_RIO enables Random Early Detection In and Out.

options ALTQ_HFSC enables the Hierarchical Fair Service Curve Packet Scheduler HFSC. For more information, refer to http://www-2.cs.cmu.edu/~hzhang/HFSC/main.html.

options ALTQ_PRIQ enables Priority Queuing (PRIQ). PRIQ will always pass traffic that is in a higher queue first.

options ALTQ_NOPCC enables SMP support for ALTQ. This option is required on SMP systems.