78 lines
5.7 KiB
HTML
78 lines
5.7 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="security" content="public" />
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<meta name="Robots" content="index,follow" />
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Layer 2 Tunnel Protocol (L2TP)" />
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<meta name="abstract" content="Use this information to learn about creating a VPN connection to secure communications between your network and remote clients." />
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<meta name="description" content="Use this information to learn about creating a VPN connection to secure communications between your network and remote clients." />
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<meta name="DC.Relation" scheme="URI" content="rzajavpnprotocols.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzajaremoteuser.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzajaremoteuser.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2000, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2000, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="rzajal2tpprotocol" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Layer 2 Tunnel Protocol (L2TP)</title>
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</head>
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<body id="rzajal2tpprotocol"><a name="rzajal2tpprotocol"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Layer 2 Tunnel Protocol (L2TP)</h1>
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<div><p>Use this information to learn about creating a VPN connection to
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secure communications between your network and remote clients.</p>
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<p>Layer 2 Tunneling Protocol (L2TP) connections, which are also called virtual
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lines, provide cost-effective access for remote users by allowing a corporate
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network server to manage the IP addresses assigned to its remote users. Further,
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L2TP connections provide secure access to your system or network when you
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use them in conjunction with IP Security (IPSec).</p>
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<p>L2TP supports two tunnel modes: the voluntary tunnel and the compulsory
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tunnel. The major difference between these two tunnel modes is the endpoint.
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On the voluntary tunnel, the tunnel ends at the remote client whereas the
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compulsory tunnel ends at the ISP.</p>
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<p>With an L2TP <span class="uicontrol">compulsory tunnel</span>, a remote host initiates
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a connection to its Internet Service Provider (ISP). The ISP then establishes
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an L2TP connection between the remote user and the corporate network. Although
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the ISP establishes the connection, you decide how to protect the traffic
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by using VPN. With a compulsory tunnel, the ISP must support LT2P.</p>
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<p>With an L2TP <span class="uicontrol">voluntary tunnel</span>, the connection is
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created by the remote user, typically by using an L2TP tunneling client. As
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a result, the remote user sends L2TP packets to its ISP which forwards them
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on to the corporate network. With a voluntary tunnel, the ISP does not need
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to support L2TP. The scenario, Protect an L2TP voluntary tunnel with IPSec
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provides you with an example of how to configure a branch office system to
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connect to its corporate network through a gateway system with an L2TP tunnel
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protected by VPN.</p>
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<p>You can view a visual presentation about the concept of <a href="rzajal2tp_pres_wrapper.htm">L2TP voluntary tunnels protected
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by IPSec</a>. This requires the <a href="http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash" target="_blank">Flash plug-in</a>. Alternatively, you can use the <a href="rzajal2tp_pres.htm">HTML version</a> of this presentation.</p>
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<p>L2TP is actually a variation of an IP encapsulation protocol. The L2TP
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tunnel is created by encapsulating an L2TP frame inside a User Datagram Protocol
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(UDP) packet, which in turn is encapsulated inside an IP packet. The source
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and destination addresses of this IP packet define the endpoints
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of the connection. Because the outer encapsulating protocol is IP, you can
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apply IPSec protocols to the composite IP packet. This protects the data that
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flows within the L2TP tunnel. You can then apply Authentication Header (AH),
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Encapsulated Security Payload (ESP), and the Internet Key Exchange (IKE) protocol
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in a straightforward way.</p>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzajavpnprotocols.htm" title="It is important that you have at least a basic knowledge of standard VPN technologies. This topic provides you with conceptual information about the protocols VPN uses in its implementation.">VPN concepts</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rzajaremoteuser.htm" title="In this scenario, you learn how to setup a connection between a branch office host and a corporate office that uses L2TP protected by IPSec. The branch office has a dynamically assigned IP address, while the corporate office has a static, globally routable IP address.">Scenario: Protect an L2TP voluntary tunnel with IPSec</a></div>
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</div>
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</div>
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</body>
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</html>
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