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