shorewall_code/Shorewall-docs/dhcp.xml

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  <articleinfo>
    <title>DHCP</title>

    <authorgroup>
      <author>
        <firstname>Tom</firstname>

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

    <pubdate>2002-11-03</pubdate>

    <copyright>
      <year>2001</year>

      <year>2002</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>If you want to Run a DHCP Server on your firewall</title>

    <itemizedlist>
      <listitem>
        <para>Specify the <quote>dhcp</quote> option on each interface to be
        served by your server in the /etc/shorewall/interfaces file. This will
        generate rules that will allow DHCP to and from your firewall system.</para>
      </listitem>

      <listitem>
        <para>When starting <quote>dhcpd</quote>, you need to list those
        interfaces on the run line. On a RedHat system, this is done by
        modifying /etc/sysconfig/dhcpd.</para>
      </listitem>
    </itemizedlist>
  </section>

  <section>
    <title>If a Firewall Interface gets its IP Address via DHCP</title>

    <itemizedlist>
      <listitem>
        <para>Specify the <quote>dhcp</quote> option for this interface in the
        <ulink url="Documentation.htm#Interfaces">/etc/shorewall/interfaces</ulink>
        file.&#x00A0;This will generate rules that will allow DHCP to and from
        your firewall system.</para>
      </listitem>

      <listitem>
        <para>If you know that the dynamic address is always going to be in
        the same subnet, you can specify the subnet address in the
        interface&#39;s entry in the <ulink url="Documentation.htm#Interfaces">/etc/shorewall/interfaces</ulink>
        file.</para>
      </listitem>

      <listitem>
        <para>If you don&#39;t know the subnet address in advance, you should
        specify <quote>detect</quote> for the interface&#39;s subnet address
        in the <ulink url="Documentation.htm#Interfaces">/etc/shorewall/interfaces</ulink>
        file and start Shorewall after the interface has started.</para>
      </listitem>

      <listitem>
        <para>In the event that the subnet address might change while
        Shorewall is started, you need to arrange for a <quote>shorewall
        refresh</quote> command to be executed when a new dynamic IP address
        gets assigned to the interface. Check your DHCP client&#39;s
        documentation.</para>
      </listitem>
    </itemizedlist>
  </section>
</article>