L2Tp Overview - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - BROADBAND ACCESS CONFIGURATION GUIDE 2010-10-12 Configuration Manual

CHAPTER 11

L2TP Overview

L2TP Overview

Copyright © 2010, Juniper Networks, Inc.
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 339
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.
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