OpenWrt Performance as a Transparent Firewall

摘要

In researching this article, I had a nasty surprise. Although in the past I had seen articles and how-tos on making transparent firewalls with OpenWrt, this mode of operation is not supported by default in the Kamikaze and Backfire releases. Reportedly, running iptables in bridging mode under OpenWrt reduces overall system performance by a whopping 40%! I proceeded writing this series anyhow, because I wanted to see for myself just how big an effect this is, and it seemed to me that the series still would be useful just for the sake of explaining how to install and use OpenWrt, and for explaining how to write iptables rules for transparent firewalls. However, at several points, I've written of my doubts as to the example OpenWrt/WRT54GL's suitability for high-bandwidth/high-availability settings.