This article provides an introduction to the netfilter/iptables system, how it works, its advantages, installing and configuring, and how to use it to configure firewalls on Linux systems to filter IP packets. The netfilter/iptables is the IP packet filtering system that is integrated with the latest 2.4.x versions of the Linux kernel. This system facilitates greater control over IP packet filtering and firewall configuration on Linux systems, be the systems connected to the Internet or a LAN, servers, or proxy servers interfacing between a LAN and the Internet. Note: Knowledge of Linux OS and experience of configuring Linux kernels will be helpful in understanding this article.

http://www-106.ibm.com/developerworks/security/library/s-netip/?t=gr,lnxm13=netIpt

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