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Try to make zone definition clearer in the Introduction
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@3915 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
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@ -130,12 +130,47 @@ dmz Demilitarized Zone</programlisting>
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<para>Zones are declared and given a type in the <ulink
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url="Documentation.htm#Zones"><filename
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class="directory">/etc/shorewall/</filename><filename>zones</filename></ulink>
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file.</para>
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file.Here is the <ulink url="Documentation.htm#Zones"><filename
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class="directory">/etc/shorewall/</filename><filename>zones</filename></ulink>
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file from the three-interface sample:</para>
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<programlisting>#ZONE TYPE OPTIONS IN OUT
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# OPTIONS OPTIONS
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fw firewall
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net ipv4
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loc ipv4
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dmz ipv4
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#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE</programlisting>
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<para>Note that Shorewall recognizes the firewall system as its own zone.
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The name of the zone designating the firewall itself is stored in the
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shell variable $<firstterm>FW</firstterm> which may be used throughout the
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Shorewall configuration to refer to the firewall zone.</para>
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The name of the zone designating the firewall itself (usually 'fw' as
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shown in the above file) is stored in the shell variable
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$<firstterm>FW</firstterm> which may be used throughout the Shorewall
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configuration to refer to the firewall zone.</para>
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<para>The simplest way to define the hosts in a zone is to associate the
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zone with a network interface using the <ulink
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url="Documentation.htm#Interfaces"><filename>/etc/shorewall/interfaces</filename></ulink>
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file. In the three-interface sample, the three zones are defined using
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that file as follows:</para>
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<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
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net eth0 detect dhcp,routefilter,norfc1918
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loc eth1 detect
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dmz eth2 detect</programlisting>
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<para>The above file defines the net zone as all IPv4 hosts interfacing to
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the firewall through eth0, the loc zone as all IPv4 hosts interfacing
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through eth1 and the dmz as all IPv4 hosts interfacing through eth2. It is
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important to note that the composition of a zone is defined in terms of a
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combination of addresses <emphasis role="bold">and</emphasis> interfaces.
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When using the <ulink
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url="Documentation.htm#Interfaces"><filename>/etc/shorewall/interfaces</filename></ulink>
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file to define a zone, all addresses are included; when you want to define
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a zone that contains a limited subset of the IPv4 address space, you use
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the <ulink
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url="Documentation.htm#Hosts"><filename>/etc/shorewall/hosts</filename></ulink>
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file.</para>
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<para>Rules about what traffic to allow and what traffic to deny are
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expressed in terms of zones. <itemizedlist spacing="compact">
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@ -232,21 +267,6 @@ $FW net ACCEPT</programlisting> The above policy will:
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</listitem>
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</itemizedlist></para>
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<para>The simplest way to define the hosts in a zone is to associate the
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zone with a network interface using the <ulink
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url="Documentation.htm#Interfaces"><filename>/etc/shorewall/interfaces</filename></ulink>
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file. In the three-interface sample, the three zones are defined using
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that file as follows:</para>
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<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
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net eth0 detect dhcp,routefilter,norfc1918
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loc eth1 detect
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dmz eth2 detect</programlisting>
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<para>The above file defines the net zone as all hosts interfacing to the
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firewall through eth0, the loc zone as all hosts interfacing through eth1
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and the dmz as all hosts interfacing through eth2.</para>
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<para>To illustrate how rules provide exceptions to policies, suppose that
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you have the polcies listed above but you want to be able to connect to
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your firewall from the internet using Secure Shell (SSH). Recall that SSH
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