Juniper JUNOSE 11.0.X MULTICAST ROUTING, Configuration Manual

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Chapter 11
L2TP Overview
Layer 2 Tunneling Protocol (L2TP) is a client-server protocol that allows Point-to-Point
Protocol (PPP) to be tunneled across a network. This chapter includes the following
topics that provide information for configuring L2TP on the Juniper Networks E Series
Broadband Services Routers.
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L2TP Overview on page 329
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L2TP Terminology on page 330
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Implementing L2TP on page 331
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Packet Fragmentation on page 333
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L2TP Platform Considerations on page 334
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L2TP Module Requirements on page 334
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Sessions and Tunnels Supported on page 335
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L2TP References on page 336
L2TP Overview
L2TP encapsulates layer 2 packets, such as PPP, for transmission across a network.
An L2TP access concentrator (LAC), configured on an access device, such as an E
Series router, receives packets from a remote client and forwards them to an L2TP
network server (LNS), on a remote network.
You can configure your router to act as an LAC in pass-through mode in which the
LAC receives packets from a remote client and then forwards them at layer 2 directly
to the LNS.
The E Series router creates tunnels dynamically by using authentication, authorization,
and accounting (AAA) authentication parameters and transmits L2TP packets to the
LNS via IP/User Datagram Protocol (UDP). Traffic travels in an L2TP
session . A tunnel
is an aggregation of one or more sessions. Figure 7 on page 330 and Figure 8 on
page 330 show the E Series router in typical LAC and LNS arrangements.
L2TP Overview
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