2003-10-08 16:55:42 +02:00
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<title>Generic Tunnels</title>
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2003-11-17 22:06:32 +01:00
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<h1 style="text-align: center;">Generic Tunnels<br>
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</h1>
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2003-10-08 16:55:42 +02:00
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Shorewall includes built-in support for a wide range of VPN solutions.
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If you have need for a tunnel type that does not have explicit support,
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you can generally describe the tunneling software using "generic
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tunnels"<br>
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<h2>Bridging two Masqueraded Networks</h2>
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<p>Suppose that we have the following situation:</p>
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<p align="center"> <img border="0" src="images/TwoNets1.png"
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width="745" height="427"> </p>
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<p align="left">We want systems in the 192.168.1.0/24 subnetwork to be
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able to 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.<br>
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</p>
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<p align="left">Suppose that you have tunneling software that uses two
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different protocols:<br>
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</p>
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<p align="left">a) TCP port 1071<br>
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b) GRE (Protocol 47)<br>
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c) The tunnel interface on system A is "tun0" and the tunnel interface
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on system B is also "tun0".<br>
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</p>
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<p align="left">On each firewall, you will need to declare a zone to
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represent the remote subnet. We'll assume that this zone is called
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'vpn' and declare it in /etc/shorewall/zones on both systems as follows.</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><strong>ZONE</strong></td>
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<td><strong>DISPLAY</strong></td>
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<td><strong>COMMENTS</strong></td>
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</tr>
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<tr>
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<td>vpn</td>
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<td>VPN</td>
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<td>Remote Subnet</td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p align="left">On system A, the 10.0.0.0/8 will comprise the <b>vpn</b>
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zone.
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In /etc/shorewall/interfaces:</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><b>ZONE</b></td>
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<td><b>INTERFACE</b></td>
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<td><b>BROADCAST</b></td>
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<td><b>OPTIONS</b></td>
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</tr>
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<tr>
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<td>vpn</td>
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<td>tun0</td>
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<td>10.255.255.255</td>
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<td> </td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p align="left">In /etc/shorewall/tunnels on system A, we need the
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following:</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><b>TYPE</b></td>
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<td><b>ZONE</b></td>
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<td><b>GATEWAY</b></td>
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<td><b>GATEWAY ZONE</b></td>
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</tr>
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<tr>
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<td>generic:tcp:1071<br>
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</td>
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<td>net</td>
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<td>134.28.54.2</td>
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<td> </td>
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</tr>
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<tr>
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<td style="vertical-align: top;">generic:47<br>
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</td>
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<td style="vertical-align: top;">net<br>
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</td>
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<td style="vertical-align: top;">134.28.54.2<br>
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</td>
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<td style="vertical-align: top;"><br>
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</td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p>These entries in /etc/shorewall/tunnels, opens the firewall so that
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TCP port 1071 and the Generalized Routing Encapsulation Protocol (47)
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will be accepted to/from the remote gateway.</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><b>ZONE</b></td>
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<td><b>INTERFACE</b></td>
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<td><b>BROADCAST</b></td>
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<td><b>OPTIONS</b></td>
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</tr>
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<tr>
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<td>vpn</td>
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<td>tun0</td>
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<td>192.168.1.255</td>
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<td> </td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p>In /etc/shorewall/tunnels on system B, we have:</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><b>TYPE</b></td>
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<td><b>ZONE</b></td>
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<td><b>GATEWAY</b></td>
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<td><b>GATEWAY ZONE</b></td>
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</tr>
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<tr>
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<td>generic:tcp:1071<br>
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</td>
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<td>net</td>
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<td>206.191.148.9</td>
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<td> </td>
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</tr>
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<tr>
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<td style="vertical-align: top;">generic:47<br>
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</td>
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<td style="vertical-align: top;">net<br>
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</td>
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<td style="vertical-align: top;">134.28.54.2<br>
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</td>
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<td style="vertical-align: top;"><br>
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</td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p align="left"> You will need to allow traffic between the "vpn" zone
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and 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:</p>
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<blockquote>
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<table border="2" cellpadding="2" style="border-collapse: collapse;">
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<tbody>
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<tr>
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<td><strong>SOURCE</strong></td>
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<td><strong>DEST</strong></td>
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<td><strong>POLICY</strong></td>
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<td><strong>LOG LEVEL</strong></td>
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</tr>
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<tr>
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<td>loc</td>
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<td>vpn</td>
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<td>ACCEPT</td>
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<td> </td>
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</tr>
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<tr>
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<td>vpn</td>
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<td>loc</td>
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<td>ACCEPT</td>
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<td> </td>
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</tr>
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</tbody>
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</table>
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</blockquote>
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<p>On both systems, restart Shorewall and start your VPN software on
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each system. The systems in the two masqueraded subnetworks
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can now talk to each other</p>
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<p><font size="2">Updated 8/9/2003 - <a href="support.htm">Tom Eastep</a>
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</font></p>
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<p><a href="copyright.htm"><font size="2">Copyright</font> <20> <font
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size="2">2001, 2002, 2003Thomas M. Eastep.</font></a></p>
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<br>
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<br>
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</body>
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</html>
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