Enable ipfw without rebooting

[scuba at centroin.com.br]

Hi all,

	What is the best way to enable/disable ipfw on a FBSD 5.x box,
without reboot?

	I.e. If I have a box that booted with 'firewall_enable="NO"' in
rc.conf, how can I enable it without reboot?

Thank you,

- Marcelo