The Sysadmin's Daily Grind: FireHOL
Off the Wall
If you don't have time to tinker with complicated firewall rules, you might want to check out the clever FireHOL approach.
There's no place like home. I can hear a quiet humming sound from the broom cupboard next to the kitchen. At least it's quiet until I open the door. When I do, I'm treated to a noise like a jet with engine trouble. Between lamp fuel, shoe polish, and miscellaneous jars stands the technology that connects me to the outside world. Beside the modems provided by my telco and an asthmatic Cisco – which is to blame for most of the noise – resides a PC old-timer, my firewall.
Originally, my manual iptables rules just handled masquerading for outgoing connections from the LAN, with a couple of custom rules for individual servers. Over time, the rules have become increasingly complex, and as they did, I found myself searching even harder for a management tool.
Finally, I found FireHOL [1]. In contrast to Firewall Builder [2], the FireHOL tool does not have a graphical user interface. Instead, you just add simple directives to a configuration file and FireHOL translates them into iptables commands.
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