forked from extern/shorewall_code
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git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@864 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
313 lines
7.8 KiB
XML
313 lines
7.8 KiB
XML
<?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 id="IPIP">
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<articleinfo>
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<title>GRE and IPIP Tunnels</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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<copyright>
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<year>2001</year>
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<year>2002</year>
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<year>2003</year>
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<holder>Thomas M. Eastep</holder>
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</copyright>
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<pubdate>2003-02-22</pubdate>
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</articleinfo>
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<warning>
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<para>GRE and IPIP Tunnels are insecure when used over the internet; use
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them at your own risk</para>
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</warning>
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<para>GRE and IPIP tunneling with Shorewall can be used to bridge two
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masqueraded networks.</para>
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<para>The simple scripts described in the <ulink url="http://ds9a.nl/lartc">Linux
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Advanced Routing and Shaping HOWTO</ulink> work fine with Shorewall.
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Shorewall also includes a tunnel script for automating tunnel configuration.
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If you have installed the RPM, the tunnel script may be found in the
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Shorewall documentation directory (usually
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/usr/share/doc/shorewall-<version>/).</para>
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<section>
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<title>Bridging two Masqueraded Networks</title>
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<para>Suppose that we have the following situation:</para>
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<graphic fileref="images/TwoNets1.png" />
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<para>We want systems in the 192.168.1.0/24 subnetwork to be able to
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communicate with the systems in the 10.0.0.0/8 network. This is
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accomplished through use of the /etc/shorewall/tunnels file, the
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/etc/shorewall/policy file and the /etc/shorewall/tunnel script that is
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included with Shorewall.</para>
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<para>The 'tunnel' script is not installed in /etc/shorewall by
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default -- If you install using the tarball, the script is included in the
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tarball; if you install using the RPM, the file is in your Shorewall
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documentation directory (normally
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/usr/share/doc/shorewall-<version>).</para>
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<para>In the /etc/shorewall/tunnel script, set the 'tunnel_type'
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parameter to the type of tunnel that you want to create.</para>
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<example>
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<title>/etc/shorewall/tunnel</title>
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<programlisting>tunnel_type=gre</programlisting>
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</example>
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<para>On each firewall, you will need to declare a zone to represent the
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remote subnet. We'll assume that this zone is called 'vpn' and
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declare it in /etc/shorewall/zones on both systems as follows.</para>
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<table>
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<title>/etc/shorewall/zones system A & B</title>
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<tgroup cols="3">
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<thead>
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<row>
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<entry align="center">ZONE</entry>
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<entry align="center">DISPLAY</entry>
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<entry align="center">COMMENTS</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>vpn</entry>
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<entry>VPN</entry>
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<entry>Remote Subnet</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>On system A, the 10.0.0.0/8 will comprise the <emphasis role="bold">vpn</emphasis>
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zone. In /etc/shorewall/interfaces:</para>
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<table>
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<title>/etc/shorewall/interfaces system A</title>
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<tgroup cols="4">
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<thead>
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<row>
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<entry align="center">ZONE</entry>
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<entry align="center">INTERFACE</entry>
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<entry align="center">BROADCAST</entry>
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<entry align="center">OPTIONS</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>vpn</entry>
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<entry>tosysb</entry>
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<entry>10.255.255.255</entry>
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<entry></entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>In /etc/shorewall/tunnels on system A, we need the following:</para>
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<table>
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<title>/etc/shorewall/tunnels system A</title>
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<tgroup cols="4">
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<thead>
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<row>
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<entry align="center">TYPE</entry>
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<entry align="center">ZONE</entry>
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<entry align="center">GATEWAY</entry>
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<entry align="center">GATEWAY ZONE</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>ipip</entry>
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<entry>net</entry>
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<entry>134.28.54.2</entry>
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<entry></entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>This entry in /etc/shorewall/tunnels, opens the firewall so that the
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IP encapsulation protocol (4) will be accepted to/from the remote gateway.</para>
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<para>In the tunnel script on system A:</para>
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<example>
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<title>tunnel script on system A</title>
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<programlisting>tunnel=tosysb
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myrealip=206.161.148.9 (for GRE tunnel only)
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myip=192.168.1.1
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hisip=10.0.0.1
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gateway=134.28.54.2
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subnet=10.0.0.0/8
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</programlisting>
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</example>
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<para>Similarly, On system B the 192.168.1.0/24 subnet will comprise the
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<emphasis role="bold">vpn</emphasis> zone. In /etc/shorewall/interfaces:</para>
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<table>
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<title>/etc/shorewall/interfaces system B</title>
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<tgroup cols="4">
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<thead>
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<row>
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<entry align="center">ZONE</entry>
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<entry align="center">INTERFACE</entry>
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<entry align="center">BROADCAST</entry>
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<entry align="center">OPTIONS</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>vpn</entry>
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<entry>tosysa</entry>
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<entry>192.168.1.255</entry>
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<entry></entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>In /etc/shorewall/tunnels on system B, we have:</para>
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<table>
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<title>/etc/shorewall/tunnels system B</title>
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<tgroup cols="4">
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<thead>
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<row>
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<entry align="center">TYPE</entry>
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<entry align="center">ZONE</entry>
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<entry align="center">GATEWAY</entry>
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<entry align="center">GATEWAY ZONE</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>ipip</entry>
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<entry>net</entry>
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<entry>206.191.148.9</entry>
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<entry></entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>And in the tunnel script on system B:</para>
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<example>
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<title> tunnel script on system B</title>
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<programlisting>tunnel=tosysa
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myrealip=134.28.54.2 (for GRE tunnel only)
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myip=10.0.0.1
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hisip=192.168.1.1
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gateway=206.191.148.9
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subnet=192.168.1.0/24</programlisting>
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</example>
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<para>You can rename the modified tunnel scripts if you like; be sure that
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they are secured so that root can execute them. </para>
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<para>You will need to allow traffic between the "vpn" zone and
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the "loc" zone on both systems -- if you simply want to admit all
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traffic in both directions, you can use the policy file:</para>
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<table>
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<title>/etc/shorewall/policy system A & B</title>
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<tgroup cols="4">
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<thead>
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<row>
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<entry align="center">SOURCE</entry>
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<entry align="center">DEST</entry>
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<entry align="center">POLICY</entry>
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<entry align="center">LOG LEVEL</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>loc</entry>
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<entry>vpn</entry>
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<entry>ACCEPT</entry>
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<entry></entry>
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</row>
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<row>
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<entry>vpn</entry>
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<entry>loc</entry>
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<entry>ACCEPT</entry>
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<entry></entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>On both systems, restart Shorewall and run the modified tunnel
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script with the "start" argument on each system. The systems in
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the two masqueraded subnetworks can now talk to each other</para>
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</section>
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</article> |