Nortel Networks manual L2TP Packet Encapsulation, Packet Encapsulation Process

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Configuring L2TP Services

L2TP Packet Encapsulation

The PC or router at the remote site sends PPP packets to the LAC. The LAC encapsulates these incoming packets in an L2TP packet and sends it across an IP network through a bidirectional tunnel. After the LNS receives the packets, it decapsulates them and terminates the PPP connection.

Figure 1-3 shows how data is encapsulated for transmission over an L2TP network.

Remote user places a call

PPP

IP

DATA

LAC

Layer 2 IP/UDP L2TP PPP IP DATA protocol

LNS

IP DATA

Data packet moves to the corporate network

L2T0005A

Figure 1-3. Packet Encapsulation Process

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Contents Configuring L2TP Services Copyright 1998 Bay Networks, Inc Bay Networks, Inc. Software License Agreement Rev Contents Chapter Starting L2TP Appendix B Configuration Examples Page Figures Page Tables Page Preface Before You BeginText Conventions Italic textAcronyms How to Get Help Bay Networks Technical PublicationsChapter L2TP Overview TopicWhat Is Tunneling? L2TP BenefitsL2TP Sessions Components of an L2TP Network Remote Host L2TP Access Concentrator LAC Remote Access Server RAS Tunnel Management Server TMS L2TP Network Server LNS Radius ServerL2TP Network Using a LAC Examples of L2TP NetworksL2TP Packet Encapsulation Packet Encapsulation ProcessMaking a Connection Across an L2TP Network Security in an L2TP Network Bay Networks L2TP Implementation Tunnel Authentication Tunnel ManagementShows tunnel authentication Radius User Authentication Radius Accounting L2TP IP Interface AddressesRemote Router Configuration Remote Router Dialing the LNSWhere to Go Next If you want to Go toPage Chapter Starting L2TP Tunnel Authentication Passwords Planning Considerations for an L2TP NetworkRadius Server Information Preparing a Configuration File Site Manager Procedure You do this System respondsTools Choose Configuration Manager Choose Local File , Remote File , orEnabling L2TP on an Unconfigured WAN Interface Subnet MaskEnabling L2TP on an Existing PPP Interface Choose Edit CircuitChoose Add/Delete Configuring L2TP Services Enabling L2TP on an Existing Frame Relay Interface Configuration is completed Site Manager Procedure Enabling L2TP on an Existing ATM InterfaceYou do this System responds Choose Group ProtocolsChoose Service Attributes Choose ProtocolsChapter Customizing L2TP Services Modifying the L2TP Protocol Configuration Choose L2TP ConfigurationModifying Radius Server Information Radius Server onChanging the LNS System Name Modifying the Number of L2TP Sessions Permitted Keeping the Remote User’s Domain Name Set the Remove Domain NameChanging the Domain Name Delimiter Set the Domain Name DelimiterEnabling Tunnel Authentication Choose Tunnel AuthenticationModifying L2TP IP Interface Addresses Choose L2TP IP InterfaceDisabling RIP Disabling L2TPCustomizing L2TP Services Deleting L2TP from a PPP InterfaceDeleting L2TP from a Frame Relay Interface Deleting L2TP from an ATM Interface Site Manager Procedure Appendix a L2TP Parameters TopicL2TP Configuration Parameters Figure A-1. L2TP Configuration List WindowParameter Enable L2TP Parameter Max L2TP SessionsParameter Receive Window Size Parameter Retransmit Timer seconds Parameter Hello Timer secondsParameter Maximum Retransmit Parameter Ack Timeout milliseconds Parameter LNS System NameParameter Radius Primary Server IP Address Parameter Radius Primary Server Password Parameter Radius Client IP AddressParameter Tunnel Flow Control Parameter Remove Domain Name Parameter Domain Name DelimiterL2TP Tunnel Security Parameters Figure A-2. L2TP Tunnel Security List WindowParameter Enable Tunnel Authentication Parameter Tunnel Authentication PasswordL2TP IP Interface Parameters Figure A-3. L2TP IP Interface List WindowParameter L2TP IP Interface Address Parameter Subnet MaskParameter RIP Enable Appendix B Configuration Examples Example 1 Remote PC Calling the Corporate NetworkConfiguring the Remote Hosts Figure B-1. L2TP Network with PCs at the Remote SiteConfiguring the LACs and the TMS Configuring the LNSDomain name baynetworks.com Parameter Name Value IP Address 192.32.16.55Data Path Through the Network L2TP IP Interface window, enter the L2TP IP addressExample 2 Remote Router Calling the Corporate Network Figure B-2. L2TP Network with Routers at the Remote SiteConfiguring the Dial-on-Demand Circuit Configuring the PPP InterfaceParameter Name Value RFC1661 Compliance Enable Appendix C Troubleshooting Problem What to DoTable C-1 Common L2TP Network Problems and Solutions Index L2TPIndex-2