If you have or can get an older machine with two NIC's, try "IPCop" http://www.ipcop.org/ or just buy a Linksys router/firewall or Dlink router/firewall.
Ralph
Or Mandrake's Multi-Network-Firewall product: http://www.mandrakesoft.com/products/mnf
-- Phil
Using Mandrake Linux 9.1 www.mandrakesoft.com
Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
