Recycling an Old Computer as an Internet Gateway and Firewall

Updated 23 November 2003

The original presentation (last updated 26 October, 2000) is in MagicPoint format. For readers' convenience, I've made some HTML conversions. The basic conversion is the kind most presentation packages make, that is, every page is an enormous image file. I also have a cleaner HTML conversion, where text remains text, and I'm considering including an embedded MagicPoint format, for those who have MagicPoint and want to view the presentation as a single file.

A handy Coyote configuration

The original presentation uses an older version of Coyote Linux, but the principles haven't changed. However, Coyote's capabilities have grown, and I now have a solution to an annoying problem.

The dial-on-demand feature is handy but, even without the nuisance of "spyware" discussed in the presentation, it seems that more and more applications (and platforms) seem to send TCP/IP traffic all day long, so it hardly ever hangs up and, when it does, it dials again almost immediately. I don't know how to identify every single source of unwanted traffic and block it.

Instead, I assembled a neatly packaged solution for folks wanting to use Coyote Linux for a dialup PPP connection in situations where demand dialing is impractical.

It uses Secure Shell (ssh) to transmit commands to connect, disconnect, or report status of the Internet connection, does all configuration when the floppy is created (no need to log in to the box to set up passwords), and includes instructions for using the firewall from GNU, Unix, and Windows boxes on the LAN. Now there's no excuse for your relatives and friends to be connecting to the Internet without a firewall.

It also accepts public keys to append to root's and dialer's authorized_keys lists. This allows password-less connections from clients running ssh-agent.

It supports using more than one ISP and switching between them easily.

Finally, it gives three beeps when it finishes booting, to announce that it's ready to serve.

Theodore B. Ruegsegger
coyote@tbr.mailshell.com