| Your FreeBSD system comes with two built-in mechanisms for
| inspecting IP packets: ipfw and ipfilter. Both have their
| own peculiar syntax for creating rulesets to determine
| which packets to allow and which packets to discard, so
| I'd like to demonstrate the usage of both. Since you can
| only run one or the other, I'll start with ipfw; once
| we've had a good look at it, I'll switch gears and move on
| to ipfilter....
Dr. Dru Lavigne has a series of three articles over on the
O'Reilly OnLamp site which deal with firewall construction
on a FreeBSD machine. Her articles rock. I find that
they are at just the right level of detail and abstraction
for someone who is just beginning to get in to a subject,
firewalls in this case. Check it out, I doubt that you
will be disappointed.