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git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@3521 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
125 lines
4.3 KiB
XML
Executable File
125 lines
4.3 KiB
XML
Executable File
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<article>
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<!--$Id$-->
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<articleinfo>
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<title>DHCP</title>
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<authorgroup>
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<author>
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<firstname>Tom</firstname>
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<surname>Eastep</surname>
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</author>
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</authorgroup>
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<pubdate>2005-11-29</pubdate>
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<copyright>
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<year>2001</year>
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<year>2002</year>
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<year>2004</year>
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<year>2005</year>
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<holder>Thomas M. Eastep</holder>
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</copyright>
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<legalnotice>
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<para>Permission is granted to copy, distribute and/or modify this
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document under the terms of the GNU Free Documentation License, Version
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1.2 or any later version published by the Free Software Foundation; with
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no Invariant Sections, with no Front-Cover, and with no Back-Cover
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Texts. A copy of the license is included in the section entitled
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<quote><ulink url="GnuCopyright.htm">GNU Free Documentation
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License</ulink></quote>.</para>
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</legalnotice>
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</articleinfo>
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<note>
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<para>For most operations, DHCP software interfaces to the Linux IP stack
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at a level below Netfilter. Hence, Netfilter (and therefore Shorewall)
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cannot be used effectively to police DHCP. The <quote>dhcp</quote>
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interface option described in this article allows for Netfilter to stay
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out of DHCP's way for those operations that can be controlled by Netfilter
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and prevents unwanted logging of DHCP-related traffic by
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Shorewall-generated Netfilter logging rules.</para>
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</note>
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<section>
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<title>If you want to Run a DHCP Server on your firewall</title>
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<itemizedlist>
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<listitem>
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<para>Specify the <quote>dhcp</quote> option on each interface to be
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served by your server in the <filename><ulink
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url="Documentation.htm#Interfaces">/etc/shorewall/interfaces</ulink></filename>
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file. This will generate rules that will allow DHCP to and from your
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firewall system.</para>
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</listitem>
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<listitem>
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<para>When starting <quote>dhcpd</quote>, you need to list those
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interfaces on the run line. On a RedHat system, this is done by
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modifying <filename>/etc/sysconfig/dhcpd</filename>.</para>
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</listitem>
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</itemizedlist>
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</section>
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<section>
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<title>If a Firewall Interface gets its IP Address via DHCP</title>
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<itemizedlist>
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<listitem>
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<para>Specify the <quote>dhcp</quote> option for this interface in the
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<ulink
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url="Documentation.htm#Interfaces"><filename>/etc/shorewall/interfaces</filename></ulink>
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file. This will generate rules that will allow DHCP to and from
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your firewall system.</para>
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</listitem>
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<listitem>
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<para>If you know that the dynamic address is always going to be in
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the same subnet, you can specify the subnet address in the interface's
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entry in the <ulink
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url="Documentation.htm#Interfaces"><filename>/etc/shorewall/interfaces</filename></ulink>
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file.</para>
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</listitem>
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<listitem>
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<para>If you don't know the subnet address in advance, you should
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specify <quote>detect</quote> for the interface's subnet address in
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the <ulink
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url="Documentation.htm#Interfaces"><filename>/etc/shorewall/interfaces</filename></ulink>
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file and start Shorewall after the interface has started.</para>
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</listitem>
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<listitem>
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<para>In the event that the subnet address might change while
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Shorewall is started, you need to arrange for a <quote>shorewall
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refresh</quote> command to be executed when a new dynamic IP address
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gets assigned to the interface. Check your DHCP client's
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documentation.</para>
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</listitem>
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</itemizedlist>
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</section>
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<section>
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<title>If you wish to pass DHCP requests and responses through a
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bridge</title>
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<itemizedlist>
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<listitem>
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<para>Specify the <quote>dhcp</quote> option for the bridge interface
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in the <ulink
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url="Documentation.htm#Interfaces"><filename>/etc/shorewall/interfaces</filename></ulink>
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file. This will generate rules that will allow DHCP to and from
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your firewall system as well as through the bridge.</para>
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</listitem>
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</itemizedlist>
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</section>
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</article> |