Jack Morgan <jack@tlug.gr.jp> wrote:

> I'm planning to install NetBSD for the first time on a SS20 and I want it
> to be a firewall to my cable modem. I'm a BSD newbie and was wondering how
> I set it up to connect throught my cable modem, which is xx.kt.home.ne.jp.

I did this with my Sparc LX, so I can tell you what I did.  First,
is this a true firewall, or just a NAT/router kind of thing.  I
bought a second 10baseT port fo my LX on eBay, as I didn't want to
plug my cable modem into a hub and see all my local traffic hit
the cable modem.  Otherwise, you could do just that, and have a
pretty simple setup as just another machine on an Ethernet segment.

If you have the second interface, it's really a simple matter of
configuring the second interface like the first, and setting the
default route to the proper place.  You can then add a route between
the interfaces to become a router and keep your local traffic away
from the cable modem, but let all your other machines use the modem
(provided they have real internet addresses).

See the Basic NetBSD Networking FAQ for basic setup stuff.  (I
assume, I don't think I've ever really looked at it.)  I have looked
at the IPFilter based Firewall HOWTO though, and it will tell you
just about all you need to know on that subject, if you need to
block or translate packets. It's on www.netbsd.org under the
documentation link at the bottom of the Networking section.  The
Basic networking page is at the top of the section.

Jon