Nortel Networks L2TP User Manual

Configuring L2TP Services

BayRS Version 13.00 Site Manager Software Version 7.00

Part No. 303532-A Rev 00 October 1998

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Preface

Before You Begin .............................................................................................................xiii

Text Convent io n s ..... ................................................ ........................................................xiv

Acronyms ......................................................................................................................... xv

Bay Networks Technical Publications ..............................................................................xvi

How to Get Help ..............................................................................................................xvi

Chapter 1 L2TP Overview

L2TP Benefits ................................................................................................................. 1-2

What Is Tunne ling? .........................................................................................................1-2

L2TP Sessions .........................................................................................................1-3

Components of an L2TP Network ..................................................................................1-4

Remote Host ............ ......................................................... .......................................1-4

L2TP Access Concentrator (LAC) ............................................................................1-5

Remote Access Server (RAS) ..................................................................................1-5

Tun nel Ma nagem ent Ser ver (TMS) ..........................................................................1-5

L2TP Network Server (LNS) ....................................................................................1-6

RADIUS Server ........................................................................................................1-6

Examples of L2TP Networks ....................................................................................1-7

L2TP Packet Encapsulation ............................................................................................1-8

Making a Connection Across an L2TP Network ......................................... ....... ....... ..... .1-9

Security in an L2TP Netw o rk ................ .................................................................. ......1-10

Bay Networks L2TP Implementation ............................................................................1-11

Tunnel Management ............................................................................................... 1 -12

Tunnel Authentication .............................................................................................1 -12

RADIUS User Authentication .................................................................................1-14

RADIUS Accounting ...............................................................................................1-15

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L2TP IP Interface Addresses .................................................................................1-15

Remote Router Configuration ................................................................................ 1 -16

Where to Go Next .........................................................................................................1-17

Chapter 2 Starting L2TP

Planning Considerations for an L2TP Network .................................... .. ....... .......... ....... .2-2

Tun nel Authentication Passwords .............................................................................2-2

RADIUS Server Information .....................................................................................2-2

Preparing a Configuration File ........................................................................................2-3

Enabling L2TP on an Unconfigured WAN Interface ........................................................2-4

Enabling L2TP on an Existing PPP Interface .................................................................2-5

Enabling L2TP on an Existing Frame Relay Interface ....................................................2-7

Enabling L2TP on an Existing ATM Interface ................................................................. 2-9

Chapter 3 Customizing L2TP Services

Modifying the L2TP Protocol Configuration .................................................................... 3-2

Modifying RADIUS Server Information ........................................................................... 3-3

Changing the LNS System Name ...................................................................................3-4

Modifying the Number of L2TP Sessions Permitted .......................................................3-5

Keeping the Remote User’s Domain Name ....................................................................3-6

Changing the Domain Name Delimiter ...........................................................................3-7

Enabling Tunne l Authentication ...................................................................................... 3-8

Modifying L2TP IP Interface Addresses .........................................................................3-9

Disabling RIP ................................................................................................................3-10

Disabling L2TP .............................................................................................................3-10

Deleting L2TP from a PPP Interface .............................................................................3-11

Deleting L2TP from a Frame Relay Interface ...............................................................3-12

Deleting L2TP from an ATM Interface ...........................................................................3 -13

Appendix A L2TP Parameters

L2TP Configuration Parameters ....................................................................................A-2

L2TP Tunnel Security Parameters ................................................................................. A-8

L2TP IP Interface Parameters .....................................................................................A-10

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Appendix B Configurati on Exampl es

Example 1: Remote PC Calling the Corporate Network ................................................ B-1

Configuring the Remote Hosts ................................................................................ B-2

Configuring the LACs and the TMS ........................................................................B-3

Configuring the LNS ................................................................................................ B-3

Data Path Through the Network ..............................................................................B-4

Example 2: Remote Router Calling the Corporate Network .......................................... B-5

Configuring the Dial-on-Demand Circuit ................................................................. B-6

Configurin g the PPP Inte r face .................................. ...............................................B-6

Appendix C Troubleshooting

Index

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Figures

Figure 1-1. L2TP Network Using a LAC .....................................................................1-7

Figure 1-2. L2TP Network Using a RAS .....................................................................1-7

Figure 1-3. Packet Encapsulation Process .................................................................1-8

Figure 1-4. Tunnel Authentication Control Messages ......................................... .. ....1-13

Figure 1-5. Remote Router Dialing the LNS .............................................................1-16

Figure A-1. L2TP Configuration List Window .............................................................A-2

Figure A-2. L2TP T unnel Security List Window .........................................................A-8

Figure A-3. L2TP IP Interface List Window .............................................................. A-10

Figure A-4. L2TP IP Interface Window ....................................................................A-10

Figure B-1. L2TP Network with PCs at the Remote Site ...........................................B-2

Figure B-2. L2TP Network with Routers at the Remote Site ..................................... B-5

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Tables

Table C-1. Common L2TP Network Problems and Solutions ..................................C-1

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This guide describes La yer 2 Tunneling Proto col (L2TP) and what you do to start and customize L2TP services on a Bay Networks® router.

Before You Begin

Before using this guide, you must complete the following procedures. For a new router:

• Ins ta ll the rout er (re fer t o the installation guide that came with your router).

• Connect the router to the network and create a configuration file (refer to

Quick-Starting Routers, Configuring BayStack Remote Access, or Connecting ASN Routers to a Network).

Preface

303532-A Rev 00

Make sure that you are running the latest version of Bay Networks BayRS Site Manager software. For information about upgrading BayRS and Site Manager, see the upgrading guide for your version of BayRS.

™

and

xiii

Configuring L2TP Services

Text Conventions

This guide uses the following text conventions:

bold text

Indicates text tha t you need to enter and command names and options. Example: Enter

Example: Use the

show ip {alerts | routes

command.

dinfo

}

italic text Indicates file and directory names, new terms, book

titles, and variables in command syntax descriptions. Where a variable is two or more words, the words are connected by an underscore. Example: If the command syntax is:

show at

valid_route

valid_route>

is one va riable and you subs titu te one value

for it.

screen text Indicates system output , fo r exa mple, prompts and

system messages. Example:

Set Ba y Netw orks Tr ap Mo nito r Fil ters

separator ( > ) Shows menu paths.

Example: Protocol s > IP identifie s the IP option on the Protocols menu.

vertical line (

) Separates choices for command keywords and

arguments. Enter only one of the choices. Do not type the vertical line when entering the command. Example: If the command syntax is:

xiv

show ip {alerts | rou tes show ip alerts

show ip routes

, you enter either:

}

, but not both.

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Acronyms

Preface

CHAP Challenge Handshake Authentication Protocol IP Internet Protocol ISDN Integra ted Services Digital Network ISP Internet Servic e Provider L2TP Layer 2 Tunneling Protocol LAC L2TP access concentrat or LAN local area network LCP Link Control Protocol LNS L2TP network server MPPP Multilink Point-to-Point Protocol PAP Password Authe ntication Protocol PPP Point-to-Poi nt Protocol

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RADIUS Remote Authentication Dial-In User Service RAS remote access server RIP Routing Informati on Protocol SCCCN start control connection connected SCCRP start control connection reply SCCRQ start control connection request TA terminal adapter TCP/IP Tra nsmission Control Protocol/Internet Protocol TMS tunnel management server UDP User Datagram Protocol VPN virtual private network WAN wide area network

Configuring L2TP Services

Bay Netwo rks Technical Publications

You can now print Bay Networks technical manuals and release notes free, directly from the Int ernet. Go to support.bayn etworks.com/libr ary/tpubs/. Fi nd the Bay Networks product for which you need doc umenta tion. Then locate the specific category and model or version for your hardware or software product. Using Adobe Acrobat Reader, you can open the manuals and release note s, sear ch for the sections you need, and print them on most standard printers. You can download Acrobat Reader free from the Adobe Systems Web site, www.adobe.com.

You can purchase Bay Networks documentation sets, CDs, and selected technic al publications through the Bay Networks Collateral Catalog. The catalog is loc ated on the World Wide Web at support.baynetworks .c om/catalog.html and is divided into sections arran ged alpha betically:

• The “CD ROMs” section lists available CDs.

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Use the “Marketing Collateral Catalog description” link to place an order and to print the order form.

How to Get Help

For product assista nce, support contracts, or informati on abou t educational services, go to the following URL:

http://www.baynetworks.com/corporate/contacts/

Or telephone the Bay Networks Technical Solutions Center at: 800-2LANWAN

xvi

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Chapter 1

L2TP Overview

The Layer 2 Tunneling Protocol (L2TP) provides remote users, such as telecommuters, mobile professionals, and personnel in remote branch offices, with dial-in access to a corporate network. L2TP enables users to create a virtual private network (VPN), whic h uses the existing physical infrastr ucture of a public network, such as the Internet, but offers the security and exclusivit y of a private network.

This chapter contains the following information:

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Topic Page

L2TP Benefits What Is Tunneling? 1-2 Components of an L2TP Network 1-4 L2TP Pac ket Encapsulation 1-8 Making a Connection Acro ss an L2TP Network 1-9 Security in an L2TP Network 1-10 Bay Networks L2TP Implementation 1-11 Where to Go Next 1-17

1-2

1-1

Configuring L2TP Services

L2TP Benefits

L2TP has seve ral advantages:

• Users and businesses can take adv antage of existing network equipment a nd resources.

Corporations do not need to maintain a nd manage remo te access servers and other special netw ork ing equipment for remote users. Instead, they c an use their existin g Interne t leased c onnections a nd resources at the Interne t Service Provider (ISP) ne twork, thereby significantly reducing corporate networking and maintenance costs.

In addition, corporations do not need to provide technical support to the remote users. Because the remote user is making a local call to the ISP, the ISP provides technic al assistance if the user has trouble making connections.

• Re mo te users can place a free local call to thei r ISP for access to the Internet, eliminating long-distance toll calls required to dial the corporate network directly.

• ISPs earn more business from corporate customer s using the equipment, thereby increasing the ISP’s revenues.

• L2TP is a standards-based protocol that provides greater interoperability with networking equipment f rom other vendors.

What Is Tunneling?

Tun neling is a way of forwarding traffic from r e mote users to a corpora te network through an IP network. A tunnel is a virtu al connection between two sites, for example, an access concentrator at the ISP network and a router at the corporate network. Tunneling across an existing public network such as the Internet creates a virtual private network that offers corporate network access to a wider range of remote users.

L2TP is a tunneling mechanism that extends the end point of the Point-to-Point Protocol (PPP) connection f rom an L2TP access concentrator (LAC) or remote access server (RAS) at the ISP network to an L2TP network server (LNS) at the corporate site.

1-2

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Multiple users can communicate thr ough a single tunnel between the same LAC and LNS pair. Each user transmits and receives data in an individual L2TP session.

The LAC brings down the tunnel for any one of the following rea sons:

• A network failure occurs.

• The LAC or other equipment at the ISP is not operating properly. If the LAC

• There are no active sessions inside the tunnel.

• The system administrator at the ISP terminates the user connection.

• The LAC is not responding to a Hello packet from the LNS.

For the LAC to rees tablish a tunnel, the remote user has to place a new call.

L2TP Sessions

L2TP Overview

fails, all tunnel users are disconnected.

An individual se ssion ends when a remote user disconnects the call, but multiple sessions can ru n inside a single tunnel.

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Packets are exchanged acr o ss an L2TP tunnel during an L2TP session. An L2TP session is c reated whe n an e nd-to-e nd WAN connection is est ablished be twee n the remote host and the LNS.

The L2TP portion of the packets sent thr ough the tunnel contains a header with a call ID field (also called a session ID) and a tunnel ID field. The call ID field, which indicate s the sess ion t hat the WAN packet belongs t o, is ne goti ated b etween the LAC and the LNS when the L2TP call is set up. The tunnel ID specifies the tunnel that the L2TP session is using.

In addition to the fi el ds in the header, the L2TP packet contain s a call serial number, which is a unique number for each L2TP call. This number matches the call to the L2TP session.

For an L2TP session, you can enable flow control. Flow control manages congestion ac ross th e conn ection, ensures that pa cke ts a re not lo st, and m akes sur e the device s at each end of the conne ction are communicating properly.

To enable flow control, se e Chapter 3

, “Customizing L2TP Services.”

1-3

Configuring L2TP Services

Components of an L2TP Network

The following sections describe the components of an L2TP network. For illustrati ons of L2TP networks, see Figures 1-1 and 1-2 on page 1-7.

Remote Host

At the remote site is the user who wants to dial in to the corpor ate network. The remote user can be located anywhere, provided that the user can dial into an ISP network using a PC or a router. The ISP provides the connection to the Int ernet.

The host at the remote site can be a PC or router that uses PPP for dial-up connections.

• If the PC or router does not have built-in L2TP software capabilities, it dia ls into a LAC, which provides a tunnel across the Internet to the corpor at e LNS.

• If the PC or router is an L2TP client, that is, it has buil t-in L2TP func tionali ty, the L2TP client software provides a tunnel through a RAS across the Internet to the corporate LNS. A LAC is unnecessary with an L2TP client.

The main differe nce between connecting an L2TP client and a nonclient is the starting point of the tunn el. For an L2TP client, the tunnel begins at the PC or router; for a non-L2TP client, the tunnel beg ins at the LAC. All tunn el s end at the LNS.

1-4

This guide’s primary focus is on an L2TP network between a remote

Note:

host that doe s not have built- in L2TP capabili ties a nd u ses a LAC, rather than a RAS.

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L2TP Access Concentrator (LAC)

The L2TP access concentrator (LAC) resides at the ISP network. The LA C establishes the L2TP tunnel between itself and the LNS.

In this guide, the term LAC refers to a remote access server with L2TP

Note:

capabilitie s. The term RAS refers to a remote access server without L2TP capabilities.

When the remote user places a call to the ISP network, this call goes to the LAC. The LAC then ne gotiates the activ ation of an L2TP tunnel with the LNS. This tunnel carries data from the remot e user to the corporate network.

For more information about the Bay Networks implementation of the LAC in an L2TP network, see “Bay Networks L2TP Implem entation

Remote Access Server (RAS)

The remote access serve r (RAS) resides at the ISP network. If the remote host is an L2TP client, the tunnel is established from the remote client through a RAS to an LNS at the corporate network. In this situation, there is no need for a LAC.

L2TP Overview

” on page 1-11.

The RAS does not establish the tunnel; it only forwa rds already tunneled data to the destination.

Tunnel Management Server (TMS)

At the ISP networ k, there needs to be a mechanism for identifying L2TP tunneled users so that the LA C can constr uct the L2TP tunnel. Bay Networks uses a mechanism called a tunnel manageme nt server (TMS); other vendors may use a different method.

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Configuring L2TP Services

L2TP Network Server (LNS)

The L2TP network server (LNS) is a router that resides at the corporate network and serves as the termina tion point for L2TP tunnels and sessions.

The LNS authenticates the PPP connection r equest and allows the end-to-end PPP tunneled connection. The LNS may also perfo rm user authentication with a RADIUS server to prevent unauthorized users from access ing the network; however, user authentication may also be done by the LNS itself.

An LNS can support multiple remote user s, each communic ating withi n their own L2TP session. The L2TP session is the virtual e nd-to-end connection over which the LAC sends dat a to the LNS.

The Bay Networks router is an LNS. For info rmation about the Bay Networks LNS, see “Bay Networks L2TP Implementation

RADIUS Server

An L2TP network may include a Remote Authentication Dial-in User Service (RADIUS) server. The RADIUS server has three main func tions in an L2TP network:

” on page 1-11.

1-6

• Authenticating the remote users

• Assigning IP addresses to the remote users

• Providing accounting services for corporate billing

The RADIUS server database centr alizes the authentication function, eliminating the need to configur e each LNS with user names and passwords. It also as signs an IP address to a remote host to identify the host . Fi nally, the RADIUS server can provide accounting services for the corporate network, calcula ting billing charges for an L2TP session.

For informatio n about the Bay Networks implementation of RADIUS user authentication and accounting, see “RADIUS User Authentication and “RADIUS Accounting” on page 1-15.

” on page 1-14

303532-A Re v 00

Examples of L2TP Networks

Figure 1-1 shows an L2TP network that uses a LAC to connect to the LNS. The

tunnel is between the LAC and the LNS.

ISP network

L2TP Overview

Remote

host

No L2TP

functionality

PPP

connection

LAC

T unnel

Data

TMS

Figure 1-1. L2TP Network Using a LAC

Figure 1-2 shows an L2TP network that use s a RAS to connect to the LNS. The

tunnel is between the PC (the L2TP client) and the LNS.

ISP network

Remote

host

T unnel

RAS

Data

Frame rela y

connection

Frame rela y

connection

Corporate network

LNS

RADIUS

server

L2T0003A

Corporate network

LNS

L2TP

client

Figure 1-2. L2TP Network Using a RAS

303532-A Rev 00

RADIUS

server

L2T0004A

1-7

Configuring L2TP Services

L2TP Packet Encapsulation

The PC or router at the remote site sends PPP packets to the LAC. The LAC encapsulates thes e incomi ng 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

network.

Layer 2 protocol

shows how data is encapsulated for transmission ove r an L2TP

Remote user places a call

PPP IP

IP/UDP

LAC

LNS

DATA

PPP

IPL2TP

DATA

1-8

IP DATA

Data packet moves to the corporate network

L2T0005A

Figure 1-3. Packet Encapsulation Process

303532-A Re v 00

Making a Connection Across an L2TP Network

The followin g steps explain how a remote user connects across an L2TP network that includes a Bay Networks LAC, TMS, and LNS (see Figure 1-1 on page 1-7):

The remote user dials a LAC at the local ISP network to establish a PPP connection to the corpora te network.

In the call, the user includes any required information, for example, a user name, including a domain name, and a password. When the user dials in, he enters a name, for example, jdoe@baynetworks.com; jdoe is the user n ame and baynetworks.com is the domain name.

The LAC receives the call and passes the domain name to the TMS. If the TMS finds a match for the domain name, a tunnel can be created. The

TMS also checks the number of current connections so that they will not exceed the maximum number allowed.

If the user is not a tunnel candidate, as determined by the domain name, the LAC assumes that the remote host is making a regular dial-in request and authenticates the user acc ordingly.

L2TP Overview

303532-A Rev 00

The LAC tries to establish an L2TP tunnel with the LNS. For the LAC to send a tunnel request to the LNS, it needs the address of the

LNS. The LAC requests the address from the TMS. It then checks for this address in its own routing table. After obtaining the address, the LAC sends a tunnel request to the LNS. The LNS may perform tunnel authentication, if configured to do so. If the LAC and LNS complete tunnel authentication successfully, the LAC establishes the tunnel.

After the tunnel is established, the LAC forwards the remote user’s name to the LNS, which ver if ies the user’s identity with the corporate RADIUS serv er.

If the RADIUS server recognizes the user name, it replies with an acknowledgm ent and an IP address that it assigns to the remote user for the duration of the call. This IP address identifies the remote user who may not have an addre ss of his own.

After the remote user is succ essfully au thentica ted, the user ha s an end-to- end PPP connection to the corporate network over the Internet.

The tunnel can now carry a user session dur ing which the LAC and the LNS exchange PPP packe ts.

1-9

Configuring L2TP Services

Security in an L2TP Network

You can configure two layers of security in an L2TP network:

• Tunnel authentication Tunnel authentication is the process of negotiating the establishment of a

tunnel between the LAC and the LNS.

• User authentication The network administr ator at the corporate site can configure a RADIUS

server with the names and passwords of authorized users. The server’s database central izes the authentication function, eli minating the need to configure each LNS with user names and passwords.

When the LNS receives a call, it forwards the user information to the RADIUS server, which verifies whet he r the user is authorized to access the network.

You can also configure the LNS to perform user authentication if a RADIUS server is not part of the network configuration.

For more information a bout the Bay Networks implementation of tunn el and user authenticati on, se e “Tunnel Authentication

Authentication” on page 1-14.

” on page 1-12 and “RADIUS User

1-10

303532-A Re v 00

Bay Networks L2TP Implementation

In an L2TP network, the Bay Networks router is the LNS. LNS soft ware operates on the BLN®, BCN®, and ASN™ platforms.

The Bay Networks LNS has the following characteristics:

• Each slot can act as an LNS, which means that one router can ha ve man y LNS interface s, each with its own address. You can have as man y LNS interfaces as there are available slots on the router.

• The LNS performs user authentication with a RADIUS server to prevent unauthorized user s from acce ssing the network.

• The LNS accepts only incoming calls; it does not place calls to the LAC.

• The Bay Networks L2TP implementation supports only IP traffic through the L2TP tunnel. The LNS supports only numbered IP addresse s.

• The router interface between the ISP and the corporate network (see

Figure 1-1

(including PPP m ultilink) , or ATM. Bay Networks r ecommends t hat you use a high-speed link, such as T1, for the lea sed connection.

on page 1-7) is a leased line operating with frame relay, PPP

L2TP Overview

303532-A Rev 00

• The LNS terminates PPP multilink and PPP encapsulated data within an L2TP packet.

• The LNS operates with the LAC implementation configured on the Bay Networks Model 5399 Remote Access Concentrator.

• The host (PC or router) dialing into the ISP network can be on the same subnet as the IP inte rface on the LNS.

• The LNS supports RIP. RIP is particularly useful when the remote host is a router, because it enables the LNS to learn routing information from the remote router.

For instructions on how to configure a Bay Networks router as an LNS, see

Chapter 2

, “Starting L2TP.”

1-11

Configuring L2TP Services

Tunnel Management

The Bay Networks tunnel management server (TMS), which resides at the ISP network, stores the TMS database. This database contains the remote users’ domain name, the IP address informati on of each LNS, and other tunnel addressing information that the network administrator configures. The LAC requests this information from the TMS to construct the L2TP tunnel.

When the LAC receives a call, it forwards the domain na me to the TMS. The domain name is th e por tion of the use r’s address that s pecif ies a p articul ar l ocation in the network. For example, if the user name is jdoe@baynetworks. com, baynetworks.com is the domain name. The TMS looks up the domain name and verifies that the remote user is an L2TP user. The TMS also provides the LAC with the addressing information required to establish a tunnel to the correct LNS.

The domain name referred to in this guide is a domain identifier that

Note:

does not foll ow a speci fi c format . It i s not related t o any Domain Na me System (DNS) protocol requirements.

Tunnel Authentication

1-12

For security purp ose s, you can en able the LNS to perform tunnel authentication. Tun nel authentication is the process of negotiating the establishment of a tunnel.

During tunnel authenti cation, the LNS identifies the L2TP client or LAC by comparing the LAC ’s tunnel authentication password with its own password. If the passwords match, the LNS permit s the LAC to establish a tunnel.

The LAC does not send the tunnel authentication password as a plain-text message. The exchange of pass words works much like the PPP Challenge Handshake Authent ication Prot ocol (CHAP). When one side r ecei v es a cha llenge, it responds with a value that is calculated based on the authentication password. The receiving side matches the value against its own calculation. If the values match, authenticat ion is successful.

Tunnel authentication occurs in both directions, which means that the LAC and LNS both try to verify the other’s identity.

303532-A Re v 00

L2TP Overview

You can enable tunnel authentication on the Bay Networks LNS. If tunnel authenticati on is disabled, which is the default, the LNS sends a default challenge response to the LA C during the authentication process so that the tunne l can be established. The LNS cannot send outgoing calls, so it cannot initiate tunnel authentication.

During tunnel authenti cation, the following exchange of messages takes place:

The LAC sends a tunnel setup message, called the start control connection reque st (SCCRQ) message to the LNS. This message includes a challenge to the LNS.

The LNS replies with a tunnel response, a chal lenge response, and its own challenge message. This is called the start control connection reply (SCCRP) message.

The LAC repli es with a challenge response that includes its tunnel authentication password. This is the start control connection connected (SCCCN) message.

If this same password is configured for the LNS, the LNS grants approval to the LAC to estab lish a tunnel.

303532-A Rev 00

Figure 1-4

shows tunnel authentication.

ISP network

PPP connection

LAC

SCCRQ

tunnel request and challenge

tunnel response, challenge response,

and LNS challenge

SCCCN

challenge response

Figure 1-4. Tunnel Authentication Control Messages

Corporate network

LNS

SCCRP

L2T0006

1-13

Configuring L2TP Services

After tunnel authent ication is complete, it does not need to be repeated for other calls to the same LA C.

RADIUS User Authentication

RADIUS user authentic ation is ena bled b y defa ult on the Bay Netw orks LNS; you must configur e this feature so that the LNS ca n validate the remote user’s identity before allowing access to the network.

The network administr ator at the corporate site must configure a RADIUS server with the names and pas swords of authorized users. When the LNS receives a call, it forwards an authentic ation request with the user information to the RADIUS server, which verifies whether the user is authorized. If the user is permitte d access to the network, the RADIUS serv er replies with an acknowledgment message and the appropriate IP address f or that user to make a connection.

The IP address that the RADIUS server assigns is essential because many remote hosts may not have their own addresses. The LNS uses the address to identify the remote host and send data to the remote user. After the session ends, the IP address becomes available for another user.

1-14

If the corporate network uses an existing RADIUS database for L2TP connections, you do not have to reconfigure the names in the databa se . The LNS automatically r emov es the doma in porti on of t he use r na me that is i ncluded a s part of the call from the LA C to the LNS. If you want to keep the domain name, you can disable this feature. For instructions, see Chapter 3

, “Customizing L2TP

Services.”

For more information about configuring Bay Networks routers as RADIUS servers, see Configuring RADIUS.

303532-A Re v 00

RADIUS Accounting

The RADIUS server can provide accounting services in addition to its authentication services. RADIUS accounting is enabled by default on the Bay Networks LNS.

The RADIUS accounting serve r calculates billing charges for an L2TP session between the remote user and the LNS . To determine these charges, the server uses information that it rec eives from the LNS, such as the status of each call and the number of packets sent during the ses sion. Using this data, the server determine s billing charge s, whic h the network administ rator can use to mana ge network costs .

The primary RADIUS accounting server can be the same server as the authentication server or it can be a different server.

For more information about RADIUS accounting, see Configuring RADIUS.

L2TP IP Interface Addresses

When configuring the Bay Networks LNS, you must configure an IP address for every slot that has an L2TP interface. This address is referred to as the L2TP IP interface address. The L2TP IP interface can be any valid IP address .

L2TP Overview

303532-A Rev 00

The L2TP IP interface address is internal to the LNS. When communicating with the remote user , the LNS associa tes the user’s IP address, which is assigned by the RADIUS server, with the L2TP IP interface address that you configured.

The L2TP IP interface address and the RA D IUS-assigned IP ad d re ss d o not have to be in the same subnet.

1-15

Configuring L2TP Services

PC 1

PC 2

LAC

192.168.18.41

192.32.25.34

192.32.25.35

Dial-in router

LNS

192.168.19.34

L2TP IP, RIP enabled

192.32.33.94

LAN interface RIP enabled

192.32.25.33

Dial-on-demand RIP enabled Dial-optimized routing enabled

192.32.25.66

L2T0009B

Remote Router Configuration

If the host at the remote site is a Bay Networks router, you may need to configure a dial-on-demand circuit for the remote router’s dial-up interface to the LAC at the ISP network.

Enable RIP on both the dial- on-demand circuit and the attache d LAN interface of the remote router, so that the LNS can learn routing information from the remote router. To avoid unnecessarily activating the circ u it beca u s e o f RI P packe t s , enable dial-optimized routing for the dial-on-demand circuit (see Figure 1-5

In addition, c onfi gure a de fault or static r oute f or the r emote r outer, which uses the next-hop address tha t corresponds to the L2TP IP interface addres s of the LN S. This de f a u l t o r st a t i c ro ute ena b l e s th e remote ro uter to deliver L2TP packets to the LNS.

1-16

Figure 1-5. Remote Router Dialing the LNS

303532-A Re v 00

Where to Go Next

Go to one of the following chap ters f or more information:

If you want to Go to

Start L2TP on a router using defa ult parameter settings. Chapter 2 Change default settings for L2TP parameters. Chapter 3 Obtain inf ormation about Site Manager parameters (this is the same

informatio n you obtain using Site Manager online Help). Review configuration examples. Appendix B Troubleshoot L2TP configuration problems. Appendix C

L2TP Overview

Appendix A

303532-A Rev 00

1-17

Chapter 2

Starting L2TP

The quickest way to star t L2TP is to enable it with the default configuration that Bay Networks software supplies. This configuration uses all available parameter defaults. You need to supply values f or sev e ral paramet ers that do not hav e default values.

This chapter includes the following information:

Topic Page

303532-A Rev 00

Planning Considerations for an L2TP Network Preparing a Configuration File 2-3 Enabling L2TP on an Unconfigured WAN Interface 2-4 Enabling L2TP on an Existing PPP Interface 2-5 Ena bling L2 T P on an Existi n g Frame Rel ay In t e rface 2-7 Enabling L2TP on an Existing ATM Interface 2-9

2-2

2-1

Configuring L2TP Services

Planning Considerations for an L2TP Network

This guide primarily e xpla ins how to configure a Bay Networks BLN, BCN, or ASN router as an LNS in an L2TP network. To successfully operate in an L2TP network, obtain the following information to conf igure the LNS.

Tunnel Authentication Passwords

If you plan to enable tunnel authentication, which is optional for the Bay Networks LNS, you must obtain the LAC password from your ISP. For more information about the authentication process, see “Tunnel Authentication” on

page 1-12.

RADIUS Server Information

The Bay Networks implementation of L2TP requires that you configure a RADIUS server to perform user authentication and to assign IP addresses to remote users.

For the RADIUS server, do the following:

2-2

• Configure the RADIUS server with user names and domain names.

• Obtain the address and password of the RADIUS server to enter in the LNS configura tion.

• Configure the RADIUS server to assign IP addresses to remote users. This address identi fies the remote user to the LNS during an L2TP sessio n. I f

the remote use r does not have a preconfigured addre ss, the only way to a ssign addresses is by the RADIUS serv e r. This address is also used for netw ork communication across the subscriber network.

For more information about configuring Bay Networks routers as RADIUS servers, see Configuring RADIUS.

303532-A Re v 00

Preparing a Configuration File

Before starting L2TP, you must create and save a configurat ion file with at least one WAN interface, for example, a synchronous or MCT1 port.

L2TP is not compatible with dial serv ices. Do not enable L2TP on the

Note:

same slot that you enable for a dial service, such as dial-on-demand, dial backup, or bandwidth-on-demand.

For informatio n about the Site Manager configuration tool and how to work with configura tion files, see Configuring and Managing Routers with Site Manager.

To open the configuration file, complete the following tasks:

Site Manager Procedure

You do this System responds

Starting L2TP

1. In the main Site Manager window, choose

Tools

2. Choose

3. Choose

Dynamic

4. Select the file and cl ick on OK. The Configuration Manager window

Configuration Manager

Local File, Remote File

. The Configuration Manager window

, or

The Tools menu opens.

opens. Site Manager prompts you for the

configuration file you want to open.

opens, displaying the router modules.

From the Configurat ion Manager window , go to one of the following sections to enable L2TP:

Section Page

Enabling L2TP on an Unconfigured WAN Interface Enabling L2TP on an Existing PPP Interface 2-5 Ena bling L2 T P on an Existi n g Frame Rel ay In t e rface 2-7 Enabling L2TP on an Existing ATM Interface 2-9

2-4

303532-A Rev 00

2-3

Configuring L2TP Services

Enabling L2TP on an Unconfigured WAN Interface

To enable L2TP on an unconfigured WAN interface, complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , choose a WAN connector.

2. Accept the default circuit name or change it, then click on OK.

3. Choose click o n OK.

4. Choose

5. Enter the IP address of the LNS (r outer), then click on OK.

6. Set the following parameters:

• RADIUS Primary Server IP Address

• RADIUS Primary Server Password

•

7. Click on OK. The L2TP Tunneling Security window

8. Click on OK. The L2TP IP I nter f ace L ist window ope ns ,

9. Set the following parameters:

• L2TP IP Interface Address

•

PPP, Frame Relay

L2TP

, then click on OK. The IP Configuration window opens.

RADIUS Client IP Address

Click on descriptions beginning on page A-5

Subnet Mask

Help

or see the parameter

, or

ATM

then

The Add Circuit window opens.

The WAN Protocols window opens.

The Select Protocols window opens.

The L2TP Configuration window opens.

opens.

followed by the L2TP IP Configuration window.

Site Manager displays a message alerting you of the time delay to create the L2TP tunnel circuits.

2-4

Click on descriptions beginning on page A-11

10.Click on OK. You return to the L2TP IP Interface List

Help

or see the parameter

window, which displays the IP interface address and the subnet mask. A message windo w opens that reads,

Configuration is completed

L2TP

(continued)

303532-A Re v 00

Starting L2TP

Site Manager Procedur e

You do this System responds

11.Click on OK.

12.Click on

Done

. You return to the Configuration Manager

(continued)

window.

Enabling L2TP on an Existing PPP Interface

To enable L2TP on an interface with PPP and IP already enabled, complete the following ta sks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , choose a WAN connector.

2. Choose

3. Choose the window.

4. Choose

5. Choose

6. Set the following parameters:

• RADIUS Primary Server IP Address

• RADIUS Primary Server Password

•

Edit Circuit Protocols

Add/Delete L2TP

RADIUS Client IP Address

. The Circuit Definition window opens.

in the top left corner of

. The Select Protocols window opens.

, then click on OK. The L2TP Configuration window opens.

The Edit Connector window opens.

The Protocols menu opens.

303532-A Rev 00

Click on descriptions beginning on page A-5

7. Click on OK. The L2TP Tunneling Security window

8. Click on OK. The L2TP IP I nter f ace L ist window ope ns ,

Help

or see the parameter

opens.

followed by the L2TP IP Configuration window.

(continued)

2-5

Configuring L2TP Services

Site Manager Procedur e

You do this System responds

9. Set the following parameters:

• L2TP IP Interface Address

• Subnet Mask

Click on descriptions beginning on page A-11

10.Click on OK. You return to the L2TP IP Interface List

11.Click on OK.

12.Click on

13.Choose

14.Choose

Help

or see the parameter

Done

. You return to the Circuit Definition

File

. The File menu opens.

Exit

. You return to the Configuration Manager

(continued)

Site Manager displays a message alerting you of the time delay to create the L2TP tunnel circuits.

window, which displays the IP interface address and the subnet mask. A message windo w opens that reads,

Configuration is completed

window.

L2TP

2-6

303532-A Re v 00

Enabling L2 TP on an Existing Frame Relay Interface

T o e nable L2TP on an in terface with frame relay and IP already enabled, complete the follo wing tasks:

Site Manager Procedure

You do this System responds

Starting L2TP

1. In the Configuration M anager window , choose a WAN connector.

2. Choose

3. Choose

4. Choose the window.

5. Choose

6. Choose

7. Set the following parameters:

• RADIUS Primary Server IP Address

• RADIUS Primary Server Password

•

8. Click on OK. The L2TP Tunneling Security window

9. Click on OK. The L2TP IP I nter f ace L ist window ope ns ,

10.Set the following parameters:

• L2TP IP Interface Address

• Subnet Mask

Edit Circuit

Services

Protocols

Add/Delete L2TP

RADIUS Client IP Address

Click on descriptions beginning on page A-5

Help

. The Frame Relay Circuit Definiti on

. The Fr ame Relay Service List window

in the top left corner of

. The Select Protocols window opens.

, then click on OK. The L2TP Configuration window opens.

or see the parameter

The Edit Connector window opens.

window opens.

opens. The Protocols menu opens.

opens.

followed by the L2TP IP Configuration window.

Site Manager displays a message alerting you of the time delay to create the L2TP tunnel circuits.

303532-A Rev 00

Click on descriptions beginning on page A-11

Help

or see the parameter

(continued)

2-7

Configuring L2TP Services

Site Manager Procedur e

You do this System responds

11.Click on OK. You return to the L2TP IP Interface List

12.Click on OK.

13.Click on

14.Click on

15.Click on

Done

. You return to the Frame Relay Service

Done

. You return to the Frame Relay Circuit

Done

. You return to the Configuration Manager

(continued)

window, which displays the IP interface address and the subnet mask. A message windo w opens that reads,

Configuration is completed

List window.

Definition win dow.

window.

L2TP

2-8

303532-A Re v 00

Enabling L2TP on an Existing ATM Interface

T o enabl e L2TP on an interface with ATM and IP already enabled, you can enable L2TP in two ways. If your interface uses a COM connector, complete the tasks in the follo wing table. If your interface uses an ATM connector, go to page 2-10.

Site Manager Procedure

You do this System responds

Starting L2TP

1. In the Configuration M anager window , choose a WAN connector.

2. Choose

3. Choose

4. Choose

5. Choose

6. Set the following parameters:

• RADIUS Primary Server IP Address

• RADIUS Primary Server Password

•

7. Click on OK. The L2TP Tunneling Security window

8. Click on OK. The L2TP IP I nter f ace L ist window ope ns ,

9. Set the following parameters:

• L2TP IP Interface Address

• Subnet Mask

10.Click on OK. You return to the L2TP IP Interface List

11.Click on OK.

Edit Circuit Group Protocols Add/Delete L2TP

RADIUS Client IP Address

Click on descriptions beginning on page A-5

Click on descriptions beginning on page A-11

Help

. The Circuit Definition window opens.

. The Group Protocols menu opens.

. The Select Protocols window opens.

, then click on OK. The L2TP Configuration window opens.

or see the parameter

The Edit Connector window opens.

opens.

followed by the L2TP IP Configuration window.

Site Manager displays a message alerting you of the time delay to create the L2TP tunnel circuits.

window, which displays the IP interface address and the subnet mask. A message windo w opens that reads,

Configuration is completed

L2TP

(continued)

303532-A Rev 00

2-9

Configuring L2TP Services

Site Manager Procedur e

You do this System responds

12.Click on

13.Choose

14.Choose

Done

. You return to the Circuit Definition

File

. The File menu opens.

Exit

. You return to the Configuration Manager

(continued)

window.

If your ATM interface uses an ATM connector, complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , choose an ATM connector.

2. Choose

3. Choose

4. Choose

5. Choose

6. Complete steps 6 previous table.

7. Click on

8. Click on

9. Click on

Service Attributes

Proto cols

Add/Delete. L2TP

Done

. The Protocols menu opens.

, then click on OK. The L2TP Configuration window opens.

through 11 in the

. You return to the ATM Servic e Re c o rd s

. You return to the E d it ATM Connecto r

. You return to the Configuration Manager

. The ATM Service Records List window

The Edit ATM Connector window opens.

opens.

The Select Protocols window opens.

Site Manager enables L2TP.

List window.

window.

2-10

303532-A Re v 00

Chapter 3

Customizing L2TP Services

When you enable L2TP, default values are in effect for most parameters (see parameter descrip tions in Appendix A, “L2TP Paramete rs”). You may want to change some of these values, depending on the requirements of your network.

This chapter includes the following information:

Topic Page

Modifying the L2TP Protocol Configuration Modifying RADIUS Server Information 3-3 Changing the LNS System Name 3-4 Modifying the Number of L2TP Sessions Permitted 3-5 Keeping the Remote User’s Domain Name 3-6 Changing the Domain Name Delimiter 3-7 Enabling Tunnel Authentication 3-8 Modifying L2TP IP Interface Addresses 3-9 Disabling RIP 3-10 Disabling L2TP 3-10 Deleting L2TP from a PPP Interface 3-11 Deleting L2TP from a F rame Relay Interface 3-12 Deleting L2TP from an ATM Interface 3-13

3-2

303532-A Rev 00

3-1

Configuring L2TP Services

Modifying the L2TP Protocol Configuration

To modify how data is transmitte d acr oss an L2TP network, such as the number, frequency, and timing of data and acknowledgment packets exchanged between the LNS and LAC, you can modify the L2TP protocol pa rameters.

To modify the L2TP protocol confi guration, complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , choose

2. Choose

3. Choose

4. Choose

5. Select an LNS entry from the list.

6. Edit any of the following parameters:

• Receive Window Size

• Retransmit Timer (seco nds)

• Maximum Retransmit

• Hello Timer (seconds)

• Ack Timeout (milliseconds)

•

7. Click on

Protocols IP

. The IP menu opens.

L2TP

L2TP Configuration

T unnel Flow Control

Click on descriptions beginning on page A-3

Done

. The L2TP menu opens.

. The L2TP Configuration List window

Help

or see the parameter

. You return to the Configuration Manager

The Protocols menu opens.

opens.

window.

3-2

303532-A Re v 00

Modifying RADIUS Server Information

If you change the address of the RADIUS serve r tha t you are usin g to authentic ate remote users and manage accounting functions, you must update the server address information on the LNS.

For more information about using a RADIUS server in an L2TP network, see “RADIUS Se rver

To modify the address of the RADIUS server, complete the follo wing tasks:

You do this System responds

” on page 1-6.

Site Manager Procedure

Customizing L2TP Services

1. In the Configuration M anager window , choose

2. Choose

3. Choose

4. Choose

5. Select an LNS entry from the list.

6. Set the following parameters:

• RADIUS Primary Server IP Address

• RADIUS Primary Server Password

•

7. Click on

Protocols IP

. The IP menu opens.

L2TP

L2TP Configuration

RADIUS Client IP Address

Click on descriptions beginning on page A-5

Done

. The L2TP menu opens.

. The L2TP Configuration List window

Help

or see the parameter

. You return to the Configuration Manager

The Protocols menu opens.

opens.

window.

You can also modify the RADIUS information in the conf iguration windows specific to RADIUS. For more information, see Configuring RADIUS.

303532-A Rev 00

3-3

Configuring L2TP Services

Changing the LNS System Name

The LNS system name is the name of the router. This name is used during tunnel setup to identify the LNS uniquely.

By default, Site Manager enters the system name that you initially configured when first accessing the router. See Configuring and Managing Routers with Site Manager f or more det ails about system information.

To change the LNS system name, complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , choose

2. Choose

3. Choose

4. Choose

5. Select an LNS entry from the list.

6. Set the Click on description on page A-5

7. Click on

Protocols IP

. The IP menu opens.

L2TP

L2TP Configuration

LNS System Name

Help

Done

. The L2TP menu opens.

. The L2TP Configuration List window

parameter.

or see the parameter

. You return to the Configuration Manager

The Protocols menu opens.

opens.

window.

3-4

303532-A Re v 00

Customizing L2TP Services

Modifying the Number of L2TP Sessions Permitted

You can modify the maximum number of active L2TP sessions that the LNS can manage. The default is 100 sessions.

For more information about L2TP sessions, see “L2TP Sessions

” on page 1-3.

To change the maximum number of L2TP sessions supported by the LNS, complete the follo wing tasks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , choose

2. Choose

3. Choose

4. Choose

5. Select an LNS entry from the list.

6. Set the Click on description on page A-3

7. Click on

Protocols IP

. The IP menu opens.

L2TP

L2TP Configuration

Max L2TP Sessions

Help

Done

. The L2TP menu opens.

. The L2TP Configuration List window

parameter.

or see the parameter

. You return to the Configuration Manager

The Protocols menu opens.

opens.

window.

303532-A Rev 00

3-5

Configuring L2TP Services

Keeping the Remote User’s Domain Name

The LNS removes the domain name from the complete user name by default, before passing it on to the RADIUS serve r for user authentication.

To keep the domain name with the user name, complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , choose

2. Choose

3. Choose

4. Choose

5. Select an LNS entry from the list.

6. Set the parameter to see the parameter description on

page A-7

7. Click on

Protocols IP

. The IP menu opens.

L2TP

L2TP Configuration

Remove Domain Name

Done

. The L2TP menu opens.

. The L2TP Configuration List window

Disable

. Click on

. You return to the Configuration Manager

Help

The Protocols menu opens.

opens.

window.

3-6

303532-A Re v 00

Changing the Domain Name Delimiter

In the complete user name there is a single-character delimiter that separat es the user name from t he domain name. By default, the LNS removes the domain name when it receives a call. The delimiter tells the LNS which characters to remove. The default delimit er is an at sign (@).

To change the delimiter, complete the following tasks:

Site Manager Procedure

You do this System responds

Customizing L2TP Services

1. In the Configuration M anager window , choose

2. Choose

3. Choose

4. Choose

5. Select an LNS entry from the list.

6. Set the parameter. Click on parameter descri pti on on pageA-7

7. Click on

Protocols IP

. The IP menu opens.

L2TP

L2TP Configuration

Domain Name Delimiter

Done

. The L2TP menu opens.

. The L2TP Configuration List window

Help

or see the

. You return to the Configuration Manager

The Protocols menu opens.

opens.

window.

303532-A Rev 00

3-7

Configuring L2TP Services

Enabling T unnel Authentication

To prevent una uthorized users from accessing the corporate network, you can enable tunnel authentication. During tunnel negotiation, the LAC sends its tunnel authentication password to the LNS. If the password is not recognized by the LNS, authentication is unsuccessful and the LAC cannot create the tunnel.

If you are using the Password Authentication Protocol (PAP) for PPP

Note:

authenticati on, do not en abl e tunnel authentication.

For more in format ion abou t t unnel authe nti cation, see “T unnel Aut hentic ation

page 1-12.

To enable tunnel authentica tion, complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , choose

2. Choose

3. Choose

4. Choose

5. Select an LNS entry from the list.

6. Set the following parameters:

• Enable Tunnel Authentication

•

7. Click on

Protocols IP

. The IP menu opens.

L2TP

Tunnel Authentication

T unnel Authentica tion Password

Click on descriptions on page A-9

Done

. The L2TP menu opens.

. The L2TP Tunnel Security Li st window

Help

or see the parameter

. You return to the Configuration Manager

The Protocols menu opens.

opens.

window.

” on

3-8

303532-A Re v 00

Modifying L2TP IP Interface Addresses

The L2TP IP Interface List window lists the L2TP IP interface addresses for each slot that has L2TP configur ed. The LNS uses the addresses internally to identify the remote sites.

For more information about the L2TP IP interface, see “L2TP IP Interface

Addresses” on page 1-16.

To change an address on the list, complete the following tasks:

Site Manager Procedure

You do this System responds

Customizing L2TP Services

1. In the Configuration M anager window , choose

2. Choose

3. Choose

4. Choose

5. Select an LNS entry from the list.

6. Click on

7. Modify the following parameters:

• L2TP IP Interface Address

• Subnet Mask

8. Click on OK. You return to the L2TP IP Interface List

9. Click on

Protocols IP

. The IP menu opens.

L2TP

L2TP IP Interface

Change

Click on descriptions beginning on page A-11

Done

. The L2TP menu opens.

. The L2TP IP Interface List window opens.

. The L2TP IP Interface window opens.

Help

or see the parameter

. You return to the Configuration Manager

The Protocols menu opens.

window. The new address appears in the list.

window.

303532-A Rev 00

3-9

Configuring L2TP Services

Disabling RIP

RIP is enabled on the LNS by default so that the LNS can learn routes from the remote dial-in router. If the LNS does not require RIP support, you can disable it.

To disable RIP, complete the following tasks:

You do this System responds

Site Manager Procedure

1. In the Configuration M anager window , choose

2. Choose

3. Choose

4. Choose

5. Select an LNS entry from the list.

6. Set the Click on description on page A-12

7. Click on

Disabling L2TP

To disable L2TP on a slot, complete the following tasks:

You do this System responds

1. In the Configuration M anager window , choose

2. Choose IP. The IP menu opens.

3. Choose

4. Choose

5. Select an LNS entry from the list.

The Protocols menu opens.

Protocols IP

. The IP menu opens.

L2TP

L2TP IP Interface

RIP Enable

Help

Done

Protocols

L2TP L2TP Configuration

. The L2TP menu opens.

. The L2TP IP Interface List window opens.

para m e ter to

or see the parameter

. You return to the Configuration Manager

. The L2TP menu opens.

Disable

Site Manager Procedure

. The L2TP Configuration List window

window.

The Protocols menu opens.

opens.

(continued)

3-10

303532-A Re v 00

Customizing L2TP Services

Site Manager Procedur e

You do this System responds

6. Set the

Disable

parameter descri pti on on pageA-3

7. Click on

Enable L2TP

. Click on

Done

parameter to

Help

or see the

. You return to the Configuration Manager

Deleting L2TP from a PPP Interface

To delete L2TP from a PPP interface, complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , click on a WAN connector configured with L2TP.

2. Choose

3. Choose

4. Choose

5. Click on

6. Click on OK. You return to the Circuit Definition

7. Choose

8. Choose

Edit Circuit Protocols Add/Delete

L2TP

File

. The File menu opens.

Exit

. You return to the Configuration Manager

. The Circuit Definition window opens.

. The Protocols menu opens.

. The Select Protocols window opens.

. Site Manager deselects L2TP.

(continued)

Site Manager disables L2TP for the slot.

window.

The Edit Connector window opens.

window.

303532-A Rev 00

3-11

Configuring L2TP Services

Deleting L2TP from a Frame Relay Interface

To delete L2TP from a frame relay interface, complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , click on a WAN connector configured with L2TP.

2. Choose

3. Choose

4. Choose the window.

5. Choose

6. Click on

7. Click on OK. You return to the Frame Relay Service

8. Click on

9. Click on

Edit Circuit

Services

Protocols

Add/Delete

L2TP

Done

. The Frame Relay Circuit Definiti on

. The Fr ame Relay Service List window

in the top left corner of

. The Select Protocols window opens.

. Site Manager deselects L2TP.

. You return to the Frame Relay Circuit

. You return to the Configuration Manager

The Edit Connector window opens.

window opens.

opens. The Protocols menu opens.

List window.

Definition win dow.

window.

3-12

303532-A Re v 00

Deleting L2TP from an ATM Interface

To delete L2TP from an ATM interface on a COM connector, complete the following ta sks:

Site Manager Procedure

You do this System responds

Customizing L2TP Services

1. In the Configuration M anager window , click on a COM connector configured with L2TP.

2. Choose

3. Choose

4. Choose

5. Click on

6. Click on OK. You return to the Circuit Definition

7. Choose

8. Choose

Edit Circuit Group Protocols Add/Delete

L2TP

File

. The File menu opens.

Exit

. You return to the Configuration Manager

. The Circuit Definition window opens.

. The Group Protocols menu opens.

. The Select Protocols window opens.

. Site Manager deselects L2TP.

The Edit Connector window opens.

window.

To delete L2TP from an ATM interface on an ATM connector, complete the following ta sks:

Site Manager Procedure

You do this System responds

1. In the Configuration M anager window , click on an ATM connector configured with L2TP.

2. Choose

3. Choose the window.

4. Choose

5. Click on

Service Attributes

Protocols

Add/Delete

L2TP

in the top left corner of

. The Select Protocols window opens.

. Site Manager deselects L2TP.

. The ATM Service Records List window

The Edit ATM Connector window opens.

opens. The Protocols menu opens.

(continued)

303532-A Rev 00

3-13

Configuring L2TP Services

Site Manager Procedur e

You do this System responds

6. Click on OK. You return to the ATM Servic e Re c o rd s

7. Click on

8. Click on

Done

. You return to the E d it ATM Connecto r

Done

. You return to the Configuration Manager

(continued)

List window.

window.

3-14

303532-A Re v 00

Appendix A

L2TP Parameters

This appendix contains the Site Manage r parameter descriptions for L2TP services. You can display the same information using Site Manager online Help. For information about the IP parameters that you set when enabling L2TP, see Configuring I P Services.

This appendix contains the following information:

T opic Page

303532-A Rev 00

L2TP Configuration Parameters L2TP Tunnel Security Parameters A-8 L2TP IP Interface Parameters A-10

For each parameter, this appendix provi des the following information:

• Parameter name

• Configuration Manager menu path

• Default setting

• Valid parameter options

• Parameter function

• Instructions for setting the parameter

• Management information base (MIB) object ID

A-2

A-1

Configuring L2TP Services

The Technician Interface allows you to modify parameters by issuing

commit

commands with the MIB object ID. This process is equivalent to modifying parameters using Site Manager. F or more inf ormation about using the T echnician Interface to access the MIB, see Using Technician Interface Software.

Caution:

The Technician Interface does not verify parameter values you enter.

Entering an invalid value can corrupt your configuration.

L2TP Configuration Parameters

The L2TP Configurati on List window (Figure A-1) contains parameters that define how L2TP sends and receives dat a .

set

and

A-2

Figure A-1. L2TP Configuration List Window

The parameter descriptions follow.

303532-A Re v 00

L2TP Parameters

Parameter: Enable L2TP

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: Enable

Options: Enable

Disable

Function: Enables or disables L2TP on this interface.

Instructions: Si te Manager automatica lly sets thi s paramete r to Enable when you selec t L2TP

as a protocol. Accept the default , Ena ble, to use L2TP. To temporarily disable L2TP, set this parameter to Disable.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.2

Parameter: Max L2TP Sessions

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: 100

Options: 1 to 100 sessions

Function: Specifies the maximum number of L2TP sessions that the LNS allows.

Instructions: Ente r the maximum number of L2TP sessions that you wa nt the LNS to support.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.16

Parameter : Receive Window Size

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: 4

Options: 1 to 7 packets

Function: Specifies the number of control pack ets that the LNS can receive from the LAC

without the LNS sending an acknowledgment packet to the LAC.

Instructions: Enter the number of packets that determine the window size, or accept the

default va lue.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.6

303532-A Rev 00

A-3

Configuring L2TP Services

Parameter : Retransm it Time r (s econ ds )

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: 1

Options: 1 to 60 seconds

Function: Indicates the number of seconds that the LNS waits for an acknowledgment

from the LAC before resending packets.

Instructions: If you are experiencing many timeouts during L2TP tunnel negotiation or

during a session, set this value to a number greater than the default. Otherwise, accept the default.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.7

Parameter: Maximum Retransmit

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: 1

Options: 1 to 60

Function: Specifies the maximum number of times the LNS retransmits packets to the

LAC.

Instructions: If you are experiencing many timeouts during L2TP tunnel negotiation or

during a session, set this value to a number greater than the default. Otherwise, accept the default.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.8

Parameter: Hello Timer (seconds)

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: 60

Options: 1 to 60 seconds

Function: Indicates t he maximum number of seconds that can elapse with out data activity

before the LNS sends a packet through the tunnel to the LAC to check the connection.

Instructions: Set this parameter to a smaller number only if the connection is not stable .

Otherwise, accept the defa ult.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.9

A-4

303532-A Re v 00

L2TP Parameters

Parameter: Ack Timeout (milliseconds)

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: 250

Options: 1 to 350 milliseconds

Function: Specifies the maximum number of milliseconds that can elapse before the LNS

sends an acknowledgm ent to the LA C th at it recei v ed an L2TP contr ol message, such as a tunnel authentication or session control message.

Instructions: If you are unsure of the stability of the connection or the L2TP session, se t this

parameter to a number smaller than the default. Otherwise, accept the default.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.10

Parameter: LNS System Name

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: BayRS

Options: The router’s system name or any name you specify

Function: Specifies the name of the LNS. This name applies to the router, not just the slot

with the LNS interface.

Instructions: Site Manager automatically enters the name from the router’s system

information. You can modify it, if you choose. If no system name is provided, the router uses BayRS.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.12

Parameter: RADIUS Primary Serv er IP Address

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: None

Options: Any 32-bit IP address

Function: Specifies the primary RADIUS server for user authentication.

Instructions: Enter the IP address of the RADIUS server. If the RADIUS server is already

configured, Site Manager automatically supplies the address.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.22.2.1.3

303532-A Rev 00

A-5

Configuring L2TP Services

Parameter: RADIUS Primary Serv er Password

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: None

Options: Any alphanumeric string, up to a maximum of 64 characters

Function: Specifies the primary RADIUS server’s password.

Instructions: Enter the password for the RADIUS server. If the RADIUS server is already

configured, Site Manager automatically supplies the passw ord.

MIB Object ID: 1.3.6.1.4.1.18.3.5.22.2.1.11

Parameter: RADIUS Client IP Address

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: None

Options: Any IP address

Function: Identifies the router acting as the LNS. This address applies for the en tire router .

Instructions: Enter the IP address of the router. If the RADIUS server is already configured,

Site Manager automaticall y supplie s the address.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.22.1.1.5

Parameter: Tunnel Flow Control

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: Disable

Options: Enable

Disable

Function: Specif ies whether the LNS uses flow control on the tunnele d data packet s. Flo w

control ensures the stable flow of data between both sides of the connection.

Instructions: To enable flow control, select Enable . Othe rwi se, accept the default, Disable.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.20

A-6

303532-A Re v 00

L2TP Parameters

Parameter: Remove Domain Name

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: Enable

Options: Enable

Disable

Function: Instructs the router whether to re move the domain name from the complete user

name before RADIUS authentication takes place. If enabled, the LNS removes the delimiter separating the use r name and the domain name and all characters to the right of the delimiter. Removing the domain name ensures that the RADIUS server c an identi fy the user without ha ving t o r econf i gure the names i n the server database.

Instructions: Accept the default, Enable, to remove the domain name from the user name.

Select Disable to keep the domain name.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.21

Parameter: Domain Name Delimiter

Path: Configuration Manager > Protocols > IP > L2TP > L2TP Configuration

Default: @

Options: A single-charact er string (for example, a colon)

Function: This character ide ntifies the delimiter used to separ ate the domain name from

the user name. This parameter is relevant only if you accept the default value, Enable, for the Remove Domain Name paramet er.

Instructions: Specify a character as a delimit er or accep t the defa ult.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.2.1.22

303532-A Rev 00

A-7

Configuring L2TP Services

L2TP Tunne l Securi ty Parameters

The L2TP Tunnel Sec urity List window (Figure A-2) contains the tunnel authentication parameters.

A-8

Figure A-2. L2TP Tunnel Sec uri t y Lis t Wi nd ow

The parameter descriptions follow.

303532-A Re v 00

L2TP Parameters

Parameter: Enable Tunnel Authentication

Path: Configuration Manager > Protocols > IP > L2TP > Tunnel Authentication

Default: Disable

Options: Enable

Disable

Function: Enables or disables the use of tunnel authentication for a slot on the LNS.

Tunnel aut hentication provides a le vel of network security to protect the corporate network from unauthorized users.

Instructions: Set this parameter to Enable for the LNS to perform tunnel authentication.

Otherwise, accept the default, Disable.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.1.1.2

Parameter: Tunnel Authentication Password

Path: Configuration Manager > Protocols > IP > L2TP > Tunnel Authentication

Default: None

Options: An alphanumeric string, up to a maximum of 40 characters

Function: Identif ies the L NS to the LAC if the de vices are u sing tunnel authentic ation. The

LAC and the LNS must share the same password to successfully complete tunnel authentication.

Instructions: Enter a password.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.23.1.1.5

303532-A Rev 00

A-9

Configuring L2TP Services

L2TP IP Interface Parameters

The L2TP IP Interface List window (Figure A-3) contains the list of IP interfaces for each slot on the router configured with L2TP.

A-10

Figure A-3. L2TP IP Interface List Window

When you click on Change , S ite Manager displays the L2TP IP Interface window

(Figure A-4).

Figure A-4. L2TP IP Interface W in dow

303532-A Re v 00

L2TP Parameters

The parameter descriptions follow.

Parameter : L 2 TP IP I nte rfa ce Ad dres s

Path: Configuration Manager > Protocols > IP > L2TP > L2TP IP Interface

Default: None

Options: Any unique IP address

Function: Specifies the IP address that identifi es the L2TP IP interface for the LNS. You

must provide an address for each slot configured as an LNS.

Instructions: Enter a unique IP address. This address applies for the entire router slot.

MIB Object ID: Not Applicable

Parameter: Subnet Mask

Path: Configuration Manager > Protocols > IP > L2TP > L2TP IP Interface

Default: None

Options: A 32-bit IP subnet mask

Function: Specifies the network and subnet portion of the L2TP IP interface address.

Site Manager automaticall y calc ulates a natural subnet mask based on the class of the network address. For example, if you enter a Class C address, the subnet mask will be 255.255.255.0.

To configure more subnets for your network, you can change this natural mask.

Instructions: Accept the assigned natural subnet mask or enter a new one. You are not

restricted to entering a natural mask. For example, if the L2TP IP address is

192.32.16.55, you can enter a subnet mask of 255.255.255.192.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.3.2.1.24.1.6

303532-A Rev 00

A-11

Configuring L2TP Services

Parameter: RIP Enable

Path: Configuration Manager > Protocols > IP > L2TP > L2TP IP Interface

Default: Enable

Options: Enable

Disable

Function: Specifies whether RIP Listen is enabled on this interface. See Configuring IP

Services for more information about RIP.

Instructions: Accept the default, Enabl e, so th at the LNS ca n learn routes from a remote

dial-in router. Select Disable to disable RIP.

MIB Object ID: 1.3.6.1.4 .1.18.3.5.3.2.2.2.1.2

A-12

303532-A Re v 00

Appendix B

Configuration Examples

This appendix prov ides tw o e xample s of L2TP networ k config urati ons. It i ncludes only those parameters that require changes from their default settings for proper configura tion. For instructions on modifying pa ramete rs, see Chapter 3, “Customizing L2TP Services.”

This appendix assumes that you are familiar with L2TP configuration proc ed ures. For information about setting up an interface on the router, see Quick-Starting Routers and Configuring and Managing Routers with Site Manager.

Example 1: Remote PC Calling the Corporate Network

Figure B-1 shows a sample L2TP network. In this network, note the following:

• Domain names are in the TMS database.

• User names and domain names are in the RADIUS server database.

• Tunnel IP interface addresses are unique for each slot.

• Frame relay is the WAN protocol for t he connection between the I SP network

and the corporate network.

303532-A Rev 00

B-1

Configuring L2TP Services

No active call from mmark; no tunnel needed

mmark@baynetworks.com

No L2TP functionality

jsmart@baynetworks.com

No L2TP functionality

Modem

ISDN

Multilink PPP

ISP network

LAC 2

TMS

LAC 1

Domain name in TMS database

baynetworks.com = 192.32.16.55

Frame rela y

T unnel

Corporate network

LNS

192.32.16.55

192.32.68.2

L2TP IP interface

IP addresses in the RADIUS server database

192.32.40.1 jsmart@baynetworks.com

192.32.40.2 mmark@baynetworks.com

Router

.17

RADIUS server

192.32.26.6 bay_private

.26.0

L2T0007B

Figure B-1. L2TP Network with PCs at the Remote Site

Configuring the Remote Hosts

The remote hosts in this network are two PCs running Windows 95. Neither PC has internal L2TP capabil ities.

In this network, one PC has a synchronous dial connection to the ISP via a modem. The other PC has a 128 Kb/s dial ISDN connection through an ISDN terminal adap t er (TA).

The user names at the PCs are mmark@baynetworks.c om and jsmart@baynetwor ks.com.

B-2

303532-A Re v 00

Configuring the LACs and the TMS

The LACs in this network are Model 5399 Remote Access Concentrators. Both devices ha ve L2TP modules installed. See Model 5399 Remote Access Concentrator documenta tion for information about configuring L2TP.

The LACs use the same TMS, which you configure with the following information:

Domain name: baynetworks.com Tunnel end point address (LNS address): 192.32.16.55 Tunnel authentication password: LAC1

Configuring the LNS

The LNS in this network is a BN router with at least two synchronous interfaces. To configure the router as an LNS:

Choose a WAN port for the slot y ou want as the LNS.

From the WAN Protocols menu, choose Frame Relay.

Configuration Examples

303532-A Rev 00

From the Select Pr otocols menu, choose IP and L2TP.

In the IP Configuration window, enter the IP address of the LNS.

Paramet e r Name Value

IP Address 192.32.16.55

In the L2TP Configuration window, enter the RADIUS server

informati on.

Paramet e r Name Value

RADIUS Primary Server IP Address 192.32.26.6 RADIUS Primary Server Password bay_private RADIUS Client IP Address 192.32.16.55

B-3

Configuring L2TP Services

In the L2TP Tunneling Security window, enable tunnel authentication.

Paramet e r Name Value

Enable Tunnel Authentication Enable Tunnel Authentication Password LAC1

In the L2TP IP Interface window, enter the L2TP IP address.

Paramet e r Name Value

L2TP IP Interf ace Address 192.32.68.2 Subnet Mask 255.255.255.0

During the L2TP session, the RADIUS server assigns the following IP addresses:

jsmart@baynetwor ks.com: 192.32.40.1 mmark@baynetworks.com: 192.32.40.2

These addresses are stor ed in the RADIUS serv er database.

Data Path Through the Network

After all components of the netw ork are configured, jsmart can place a call to the local ISP. The LAC that receiv es this call sends the user name to the TMS, which verifies the domain name and address and sends this information back to the LAC so that it can forward the data.

The LAC then ne gotiates the initiation of the tunnel with the LNS, and the tunnel is brought up. The LNS then authenticates jsmart@baynetworks.com with the RADIUS server. After the RADIUS server grants access, it assigns the address

192.32.40.1 to jsmart, to inc lude the remote host (jsmart’s PC) in the virtual private network.

Data now passes through the tunnel from jsmart’s PC to the LNS for the duration of the L2TP session. When jsmart disconnects the call, the session is terminated. If no other active sessions are using the tunnel, the tunnel is brought down.

B-4

303532-A Re v 00

Configuration Examples

Example 2: Remote Router Calling the Corporate Network

Figure B-2 shows a network with two BayStack™ AN® routers at the r emote site.

The AN routers are us ing dial-o n -demand servi ce fo r dia l- up connections. In this network, note the following:

• PPP is the WAN protocol for the conne ction between the ISP ne twork and the

corporate network.

• For the LNS configuration, you do not need to configure a static route for the

remote router’s network because the LNS can learn the rout e using RIP.

• The IP network addresses are assigned as follows:

jsmart@bay.com: 192.32.40.1 mmark@bay.com: 192.32.40.2

No active call from mmark;

no tunnel needed

mmark@bay .com

No L2TP functionality

jsmart@bay .com

No L2TP functionality

Modem

ISDN

Multilink PPP

ISP network

LAC 2

TMS

LAC 1

Domain name in TMS database

bay .com = 192.32.16.55

LNS

192.32.16.55

PPP

T unnel

192.32.40.254

L2TP IP interface

IP addresses in the RADIUS server database

192.32.40.1 jsmart@bay .com

192.32.40.2 mmark@bay .com

Corporate network

.17

RADIUS server

192.32.26.6 bay_private

Router

.26.0

L2T0008B

Figure B-2 . L2TP Network with Rout ers at the R em ote Site

The LNS configurat ion in this e xample is the same as in Example 1; ho we v er , you must modify the confi guration of the remote AN router. Go to the next sections.

303532-A Rev 00

B-5

Configuring L2TP Services

Configuring the Dial-on-Demand Circuit

Modify the dial-on-demand circuit configuration for the AN routers as follows:

In the Conf igurat ion Man ager windo w, choose Dialu p > Deman d Cir cuit s

> Demand Pools > PPP Circuits > PPP Demand Circuits to display the PPP Demand Circuits window.

Disable outbound authentication.

Paramet e r Name Value

Outbound Aut hentication Disable CHAP Local Name jsmart@bay.com Dial Optimized Routing Enabled

Enable RIP on the dial-on-demand circuit.

Configure default or static routes for the PC LAN to the L2TP IP

interface.

For more information about dial-on-demand, see Configuring Dial Services.

Configuring the PPP Interface

Modify the PPP interface configuration for the AN routers as follows:

In the Configuration Manager window, choose Protocols > PPP >

Interfaces to display the PPP Interface List window. Select the PPP interface to the ISP network.

Click on Lines to display the PPP Line List window.

Enable RFC 1661 compliance.

Paramet e r Name Value

RFC1661 Compliance Enable

For more information about PPP, see Configuring PPP Services.

B-6

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Appendix C

Troubleshooting

T o moni tor your L2TP network and solv e problems that may oc cur , fir st check the event log file for any messages recorded by the LNS. For information about viewing and reading event messages, see Event Messages for Routers and Configuring and Managing Routers with Site Manager.

Table C-1

provides troubleshoo ting solutions for common problems with your

L2TP network.

T able C-1. Common L2TP Network Problems and Solutions

Problem What to Do

L2TP tunnel did not initiate. Check whether y ou ena bled tunn el authe nticat ion for

the LNS on that slot.

If authentication is enabled, make sure that the authentication p ass w ord is the same for the LA C and the LNS.

You can also check the tunnel statist ics, which are automatically enabled on the LNS.

L2TP host (PC or router) cannot reach the corporate network through the established connection.

Check the address and user authentication information configured in the RADIUS server database.

(continued)

303532-A Rev 00

C-1

Configuring L2TP Services

T able C-1. Common L2TP Network Problems and Solutions

Problem What to Do

L2TP session is not activ e. The LNS failed to negoti ate the PPP LCP options.

Reconfigure the host at the remote site dialing in to the ISP.

For a Bay Networks router at the remote site, check the PPP MRU/MRRU size. The LNS supports an MRU/MRUU size of 1500 only.

Use the follo wing guidelines to configure a Bay Networks router at the remote site:

• For router software versions up to and including

11.02/rel, use an MTU size of 1510, which is the default.

• For router software versions 11.02/rev and later

RFC1661 Compliance

Bay Netw orks rout er at the re mote site cannot tunnel into the corporate network.

set the PPP par ameter Enable.

You can also check the session statist ics, which are automatically enabled on the LNS.

Check the IP address assigned by the RADIUS server. There may be a mismatch between the address of the remote ro uter dialing in to the LAC and the address that the RADIUS serve r assigns.

(continued)

C-2

For example, router A dials in with its IP address of

1.1.1.3 and the RADIUS server assigns an incorrect IP address of 1.1.1.5.

303532-A Re v 00

Index

accounting, RADIUS, 1-15 Ack Timeout (milliseconds) param eter, A -5 acrony m s , xv

Bay Networ ks LN S. See LNS

configuration examp les, B-1 configuration file, requirem ents, 2-3 conventions, text, xiv

deleting L2TP

from ATM, 3-13 from frame rela y, 3-12

from PPP, 3-11 disabling L2TP, 3-10 Domain Name Delimiter parameter, A-7 domain name, descripti on, 1-12

educational services, xvi Enable L2TP parameter, A-3 Enable Tunnel Authentication parameter, A-9

Hello Timer (seconds) parameter, A-4

L2TP

Bay Networks implementat ion, 1-11 customizing configuration, 3-1 data transmission across network, 1-9 deleting, ATM interface, 3-13 deleting, frame relay interface, 3-12 deleting, PPP interface, 3-11 descri ption, 1-1 disabling, 3-10 network components, 1-4 packet encapsulation, 1-8 parameter descriptions, A-1 parameters, modifying, 3-2 purpose, 1-2 starting, 2-3

troubleshooting, C-1 L2TP access concentrator. See LAC L2TP IP In terface Address parameter, A-11 L2TP IP interface address, modifying, 3-9 L2TP networ k server. See LNS LAC

configuration example, B-3

descri ption, 1-5

tunnel authentication, security, 1-12 Layer 2 T unneling Protocol. See L2TP LNS

Bay Networks implementat ion, 1-11

changing RADIUS server address, 3-3

changing system name, 3-4

configuration example, B-3

configuring router as, 2-3

customizing parameter s, 3-1

descri ption, 1-6

enabling tunnel authen tication, 3-8

303532-A Rev 00

Index-1

LNS (conti nued)

L2TP security, 1-10 modifyi ng protocol configuration, 3-2

operating with LACs, 1-11 LNS System Name parameter, A-5 LNS system name, changing, 3-4

Max L2TP Sessions parameter, A-3 Maximum Retransmit parameter, A-4

packet encapsulation, L2TP, 1-8 parameters

customizing, 3-1

descri ptions, A-1

Nortel Networks L2TP User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Configuring L2TP Services

Contents

Figures

Tables

Before You Begin

Preface

Text Conventions

Acronyms

Bay Netwo rks Technical Publications

How to Get Help

L2TP Benefits

What Is Tunneling?

L2TP 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 Server

Examples of L2TP Networks

L2TP Packet Encapsulation

Making a Connection Across an L2TP Network

Security in an L2TP Network

Bay Networks L2TP Implementation

Tunnel Management

Tunnel Authentication

RADIUS User Authentication

RADIUS Accounting

L2TP IP Interface Addresses

Remote Router Configuration

Where to Go Next

Planning Considerations for an L2TP Network

Tunnel Authentication Passwords

RADIUS Server Information

Preparing a Configuration File

Enabling L2TP on an Unconfigured WAN Interface

Enabling L2TP on an Existing PPP Interface

Enabling L2 TP on an Existing Frame Relay Interface

Enabling L2TP on an Existing ATM Interface

Modifying the L2TP Protocol Configuration

Modifying RADIUS Server Information

Changing the LNS System Name

Modifying the Number of L2TP Sessions Permitted

Keeping the Remote User’s Domain Name

Changing the Domain Name Delimiter

Enabling T unnel Authentication

Modifying L2TP IP Interface Addresses

Disabling RIP

Disabling L2TP

Deleting L2TP from a PPP Interface

Deleting L2TP from a Frame Relay Interface

Deleting L2TP from an ATM Interface

L2TP Configuration Parameters

L2TP Tunne l Securi ty Parameters

L2TP IP Interface Parameters

Example 1: Remote PC Calling the Corporate Network

Configuring the Remote Hosts

Configuring the LACs and the TMS

Configuring the LNS

Data Path Through the Network

Example 2: Remote Router Calling the Corporate Network

Configuring the Dial-on-Demand Circuit

Configuring the PPP Interface

Index