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<h1 align="center"><font color="#FFFFFF">VPN</font></h1>
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<p>It is often the case that a system behind the firewall needs to be able to
access a remote network through Virtual Private Networking (VPN). The two most
common means for doing this are IPSEC and PPTP. The basic setup is shown in the
following diagram:</p>
<p align="center"><img border="0" src="images/VPN.png" width="568" height="796"></p>
<p align="left">A system with an RFC 1918 address needs to access a remote
network through a remote gateway. For this example, we will assume that the
local system has IP address 192.168.1.12 and that the remote gateway has IP
address 192.0.2.224.</p>
<p align="left">If PPTP is being used, there are no firewall requirements beyond
the default loc->net ACCEPT policy. There is one restriction however: Only one
local system at a time can be connected to a single remote gateway unless you
patch your kernel from the 'Patch-o-matic' patches available at
<a href="http://www.netfilter.org">http://www.netfilter.org</a>. </p>
<p align="left">If IPSEC is being used then there are firewall configuration
requirements as follows:</p>
<blockquote>
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<td height="38"><u><b>ACTION</b></u></td>
<td height="38"><u><b>SOURCE</b></u></td>
<td height="38"><u><b>DESTINATION</b></u></td>
<td height="38"><u><b>PROTOCOL</b></u></td>
<td height="38"><u><b>PORT</b></u></td>
<td height="38"><u><b>CLIENT<br>
PORT</b></u></td>
<td height="38"><u><b>ORIGINAL<br>
DEST</b></u></td>
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<td height="19">DNAT</td>
<td height="19">net:192.0.2.224</td>
<td height="19">loc:192.168.1.12</td>
<td height="19">50</td>
<td height="19"> </td>
<td height="19"> </td>
<td height="19"> </td>
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<td height="19">DNAT</td>
<td height="19">net:192.0.2.224</td>
<td height="19">loc:192.168.1.12</td>
<td height="19">udp</td>
<td height="19">500</td>
<td height="19"> </td>
<td height="19"> </td>
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</blockquote>
<p>If you want to be able to give access to all of your local systems to the
remote network, you should consider running a VPN client on your firewall. As
starting points, see
<a href="http://www.shorewall.net/Documentation.htm#Tunnels">
http://www.shorewall.net/Documentation.htm#Tunnels</a> or
<a href="http://www.shorewall.net/PPTP.htm">http://www.shorewall.net/PPTP.htm</a>.</p>
<p><font size="2">Last modified 8/27/2002 - <a href="support.htm">Tom
Eastep</a></font><p><font face="Trebuchet MS"><a href="copyright.htm">
<font size="2">Copyright</font> � <font size="2">2002 Thomas M. Eastep.</font></a></font><p> </p>
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