Firewall Builder

Here I present an abbreviated explanation of the process of creating firewall and cluster objects. More detailed step-by-step guides are available in sections “Firewall Object” and “Cluster Object” of the Firewall Builder Users Guide.

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This article continues mini-series started with the post Introduction to Firewall Builder 4.0. This article is also available as a section in the “Firewall Builder Cookbook” chapter of Firewall Builder Users Guide 4.0.

Firewall Builder 4.0 is currently in beta testing phase. If you find it interesting after reading this post, please download and try it out. Source code archives, binary deb and rpm packages for popular Linux distributions and commercially distributed Windows and Mac OS X packages are available for download here.

In this post I demonstrate how Firewall Builder can be used to generate firewall configuration for a clustered web server with multiple virtual IP addresses. The firewall is running on each web server in the cluster. This example assumes the cluster is built with heartbeat using “old” style configuration files, but which high availability software is used to build the cluster is not really essential. I start with the setup that consists of two identical servers running Linux but in the end of the article I am going to demonstrate how this configuration can be converted to OpenBSD with CARP.

This entry is part 1 of 4 in the series Linux Firewall Cluster Configuration with Firewall Builder v4.:

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Now that all objects are ready and heartbeat is configured on the machines, we can move on and build some firewall rules. Since this is a cluster configuration, all rules go into the rule set objects that belong to the cluster rather than its member firewalls.

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This is the first article in the mini-series of two articles about Firewall Builder.

Systems administrators have a choice of modern Open Source and commercial firewall platforms at their disposal. They could use netfilter/iptables on Linux, PF, ipfilter, ipfw on OpenBSD and FreeBSD, Cisco ASA (PIX) and other commercial solutions. All these are powerful implementations with rich feature set and good performance. Unfortunately, managing security policy manually with all of these remains non-trivial task for several reasons. Even though the configuration language can be complex and overwhelming with its multitude of features and options, this is not the most difficult problem in my opinion. Administrator who manages netfilter/iptables, PF or Cisco firewall all the time quickly becomes an expert in their platform of choice. To do the job right, they need to understand internal path of the packet inside Linux or BSD kernel and its interaction with different parts of packet filtering engine. Things get significantly more difficult in the installations using different OS and platforms where the administrator needs to switch from netfilter/iptables to PF to Cisco routers and ASA to implement coordinated changes across multiple devices. This is where making changes get complicated and probability of human error increases. Unfortunately typos and more significant errors in firewall or router access list configurations lead to either service downtime or security problems, both expensive in terms of damage and time required to fix.

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