Internet standards and good engineering practice prohibit us from
providing packet forwarding by default in FreeBSD. You can
however enable this feature by changing the following variable to
YES in rc.conf:
gateway_enable=YES # Set to YES if this host will be a gateway
This option will put the sysctl variable
net.inet.ip.forwarding to 1.
In most cases, you will also need to run a routing process to
tell other systems on your network about your router; FreeBSD
comes with the standard BSD routing daemon
routed, or for more complex situations you may want to try
GaTeD (available by FTP from ftp.gated.Merit.EDU) which
supports FreeBSD as of 3_5Alpha7.
It is our duty to warn you that, even when FreeBSD is configured in this way, it does not completely comply with the Internet standard requirements for routers; however, it comes close enough for ordinary usage.