In this three-part series, Pawel Leszek looks at firewall products for Linux. Part 1 is all about open source solutions. Part 2 will cover commercial products, while Part 3 will take a look at firewall appliances. The standard firewalling support in . . .
In this three-part series, Pawel Leszek looks at firewall products for Linux. Part 1 is all about open source solutions. Part 2 will cover commercial products, while Part 3 will take a look at firewall appliances. The standard firewalling support in the Linux kernel is built upon two components -- ipchains and IP Masquerading. Both features are included in standard kernel distributions. Ipchains is a mechanism for filtering IP packets; its inclusion means that any flavor of Linux can be configured to run as a filtering gateway/firewall almost right out of the box. The second important firewalling component in the kernel is IP Masquerading -- a network address translation (NAT) implementation feature with which you can hide real IP addresses used in an internal network so you can use nonrouting IP addresses in your LAN. If you want to set up IP Masquerading, you will need to use the ipchains command-line tool.

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