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<article id="shorewall_prerequisites">
  <!--$Id$-->

  <articleinfo>
    <title>Shorewall Requirements</title>

    <author>
      <firstname>Tom</firstname>

      <surname>Eastep</surname>
    </author>

    <pubdate>2005-03-22</pubdate>

    <copyright>
      <year>2001-2005</year>

      <holder>Thomas M Eastep</holder>
    </copyright>

    <legalnotice>
      <para>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
      <quote><ulink url="GnuCopyright.htm">GNU Free Documentation
      License</ulink></quote>.</para>
    </legalnotice>
  </articleinfo>

  <section>
    <title>Shorewall Requires:</title>

    <itemizedlist>
      <listitem>
        <para>A kernel that supports netfilter. I've tested with 2.4.2 -
        2.6.11. Check <ulink url="kernel.htm">here</ulink> for kernel
        configuration information.</para>
      </listitem>

      <listitem>
        <para>iptables 1.2 or later (but I recommend at least version
        1.2.9)</para>
      </listitem>

      <listitem>
        <para>Iproute (<quote>ip</quote> utility). The iproute package is
        included with most distributions but may not be installed by default.
        The official download site is <ulink type="remote"
        url="ftp://ftp.inr.ac.ru/ip-routing">http://developer.osdl.org/dev/iproute2/download/</ulink>.</para>
      </listitem>

      <listitem>
        <para>A Bourne shell or derivative such as bash or ash. This shell
        must have correct support for variable expansion formats
        ${<emphasis>variable%pattern</emphasis>},
        ${<emphasis>variable%%pattern</emphasis>},
        ${<emphasis>variable#pattern</emphasis>} and
        ${<emphasis>variable##pattern</emphasis>}.</para>
      </listitem>

      <listitem>
        <para>Your shell must produce a sensible result when a number n (128
        &lt;= n &lt;= 255) is left shifted by 24 bits. You can check this at a
        shell prompt by:<itemizedlist>
            <listitem>
              <para>echo $((128 &lt;&lt; 24))</para>
            </listitem>

            <listitem>
              <para>The result must be either 2147483648 or
              -2147483648.</para>
            </listitem>
          </itemizedlist></para>
      </listitem>

      <listitem>
        <para>The firewall monitoring display is greatly improved if you have
        awk (gawk) installed.</para>
      </listitem>
    </itemizedlist>
  </section>
</article>