Tom Eastep 2005-05-12 2001-2005 Thomas M Eastep Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover, and with no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.

A Linux kernel that supports netfilter (No, it won't work on BSD or Solaris). I've tested with 2.4.2 - 2.6.11. Check here for kernel configuration information. iptables 1.2 or later (but I recommend at least version 1.2.9) Iproute (ip utility). The iproute package is included with most distributions but may not be installed by default. The official download site is http://developer.osdl.org/dev/iproute2/download/. A Bourne shell or derivative such as bash or ash. This shell must have correct support for variable expansion formats ${variable%pattern}, ${variable%%pattern}, ${variable#pattern} and ${variable##pattern}. Your shell must produce a sensible result when a number n (128 <= n <= 255) is left shifted by 24 bits. You can check this at a shell prompt by: echo $((128 << 24)) The result must be either 2147483648 or -2147483648. The firewall monitoring display is greatly improved if you have awk (gawk) installed.