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Chapter 11
L2TP Overview
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.
L2TP Overview on page 335
L2TP Terminology on page 336
Implementing L2TP on page 337
Packet Fragmentation on page 339
L2TP Platform Considerations on page 340
L2TP Module Requirements on page 340
Sessions and Tunnels Supported on page 341
L2TP References on page 342
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 336 and Figure 8 on
page 336 show the E Series router in typical LAC and LNS arrangements.
335
L2TP Overview
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Troubleshooting
