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NAME

     ipfw — IP packet filter and traffic accounting

SYNOPSIS

     To compile ipfw into the kernel, place the following option in the kernel configuration
     file:

           options IPFIREWALL

     Other kernel options related to ipfw which may also be useful are:

           options IPFIREWALL_DEFAULT_TO_ACCEPT
           options IPFIREWALL_FORWARD
           options IPFIREWALL_VERBOSE
           options IPFIREWALL_VERBOSE_LIMIT=100

     To load ipfw as a module at boot time, add the following line into the loader.conf(5) file:

           ipfw_load="YES"

DESCRIPTION

     The ipfw system facility allows filtering, redirecting, and other operations on IP packets
     travelling through network interfaces.

     The default behavior of ipfw is to block all incoming and outgoing traffic.  This behavior
     can be modified, to allow all traffic through the ipfw firewall by default, by enabling the
     IPFIREWALL_DEFAULT_TO_ACCEPT kernel option.  This option may be useful when configuring ipfw
     for the first time.  If the default ipfw behavior is to allow everything, it is easier to
     cope with firewall-tuning mistakes which may accidentally block all traffic.

     To enable logging of packets passing through ipfw, enable the IPFIREWALL_VERBOSE kernel
     option.  The IPFIREWALL_VERBOSE_LIMIT option will prevent syslogd(8) from flooding system
     logs or causing local Denial of Service.  This option may be set to the number of packets
     which will be logged on a per-entry basis before the entry is rate-limited.

     Policy routing and transparent forwarding features of ipfw can be enabled by
     IPFIREWALL_FORWARD kernel option.

     The user interface for ipfw is implemented by the ipfw(8) utility, so please refer to the
     ipfw(8) manpage for a complete description of the ipfw capabilities and how to use it.

SEE ALSO

     setsockopt(2), divert(4), ip(4), ipfw(8), sysctl(8), syslogd(8), pfil(9)