Paranoid Penguin - Building a Transparent Firewall with Linux, Part I

Yes, you still need a firewall. How about a transparent one?

But, that will have to wait until next time. Hopefully, you now understand the difference between a standard, routing firewall and a transparent, bridging firewall. In my next column, I'll sketch out an example usage scenario (conceptually very similar to the network in Figure 3), describe a couple different approaches to selecting Linux firewall hardware and begin showing how to configure a transparent firewall, starting with bridge/switch setup. Until then, be safe!

Mick Bauer ( is Network Security Architect for one of the US's largest banks. He is the author of the O'Reilly book Linux Server Security, 2nd edition (formerly called Building Secure Servers With Linux), an occasional presenter at information security conferences and composer of the “Network Engineering Polka”.