[Strix]

I have an iMac connected to the internet via an X-modem CE. The iMac has an airport card installed, and acts as a software base station to two iBooks.

All computers are running MacOS X 10.3.5

The X-modem is set to NAT so that the internet connection can be shared.

The problem is how to I configure the OS X firewall (in sharing preferences) so that all computers can safely access the internet? I've tried switching on the firewall but this blocks access for the iBooks!

I want to be able to run Safari, Mail and Entourage, so what ports would have to be set up on the firewall to allow access? And does the X-Modem need to be set up other than NAT switched on?

I am also assuming that I only need to set up the firewall on the iMac as this is the one plugged into the internet.

Any suggestions?

[Xeo]

The X-modem is your firewall. There no good reason to turn on OS X's built-in firewall unless you are forwarding all ports via DMZ or something. So you could just turn on sharing and be done with it. However, if you want the firewall on, I think the following could help.

I did a quick search and found this article over at Mac OS X Hints. It seems to say that the guy is using Brickhouse to configure the firewall and he has wireless clients, similar to what you want. Keep in mind, it just configures the built-in firewall so you aren't installing any new software, just a GUI to existing stuff. If you are interested in having a firewall running on your Mac, you are better off using Brickhouse to configure it anyway.

Now, looking at the Brickhouse FAQ, there are some extra hoops to jump through to get internet sharing to work properly.

You could potentially just jump through those hoops and skip the Brickhouse stuff, but then you'd be customizing it on the fly. Either way, it's up to you.

But like I said, as long as you are forwarding only specific ports from your modem, that is enough of a firewall. Any time you are behind NAT makes breaking through to a computer all the more difficult.