Avaya LT2P User Manual

Conﬁguring L2TP Services

BayRS V ersion 12.10 Site Manager Software Version 6.10

Part No. 300016-A Rev. 00 February 1998

4401 Great America Parkway 8 Federal Street Santa Clara, CA 95054 Billerica, MA 01821

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Notwithstanding any other license agreement that may pertain to, or accompany the delivery of, this computer software, the rights of the United States Government regarding its use, reproduction, and disclosure are as set forth in the Commercial Computer Software-Restricted Rights clause at FAR 52.227-19.

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300016-A Rev. 00

About This Guide

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

Conventions .....................................................................................................................xiv

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

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

Bay Networks Customer Service .....................................................................................xvi

How to Get Help .............................................................................................................xvii

Bay Networks Educational Services ...............................................................................xvii

Chapter 1 L2TP Overview

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

What Is Tunneling? .........................................................................................................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

Tunnel Management Server (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 Network ........................................................................................1-10

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

Tunnel Management ...............................................................................................1-11

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

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

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RADIUS Accounting ...............................................................................................1-14

Assigned User Network Addresses .......................................................................1-15

Where to Go Next .........................................................................................................1-15

Chapter 2 Starting L2TP

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

Tunnel 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

Using the MIB Object ID .................................................................................................3-2

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

Enabling Tunnel Authentication .......................................................................................3-6

Modifying the Assigned User Network List .....................................................................3-7

Disabling L2TP ...............................................................................................................3-8

Deleting L2TP from a PPP Interface ..............................................................................3-9

Deleting L2TP from a Frame Relay Interface .................................................................3-9

Deleting L2TP from an ATM Interface ...........................................................................3-10

Appendix A L2TP Parameters

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

L2TP Tunnel Security Parameters .................................................................................A-7

Assigned User Network Parameters ..............................................................................A-9

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Appendix B Conﬁguration Examples

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

Dial-on-Demand Circuit Conﬁguration .................................................................... B-6

PPP Interface Conﬁguration .................................................................................... B-6

Adjacent Host Conﬁguration ................................................................................... B-6

Appendix C Troubleshooting

Index

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vii

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

Figure A-2. L2TP Tunnel Security List Window .......................................................... A-7

Figure A-3. Assigned User Network List Window ...................................................... A-9

Figure A-4. Assigned User Network Window ............................................................. A-9

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 B-1. IP Address Parameter ............................................................................. B-3

Table B-2. RADIUS Server Parameters ...................................................................B-3

Table B-3. Tunnel Authentication Parameters .......................................................... B-4

Table B-4. Assigned User Network Parameters ....................................................... B-4

Table B-5. PPP Demand Circuit Parameters ........................................................... B-6

Table B-6. PPP Line List Parameter ......................................................................... B-6

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

300016-A Rev. 00

About This Guide

If you are responsible for conﬁguring L2TP, you need to read this guide.

If you want to Go to

Learn about L2TP and the Bay Networks implementation of L2TP. Chapter 1 Start L2TP on a router using default parameter settings. Chapter 2 Change default settings for L2TP parameters. Chapter 3 Obtain information about Site Manager parameters (this is the same

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

Appendix A

Before Y ou Begin

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

• Install the router (refer to 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 ASN Routers to a Network)

Make sure that you are running the latest version of Bay Networks® Site Manager and router software. For instructions, refer to the

Change Notice

300016-A Rev. 00

, or

Connecting

BayRS Version 12.10 Document

xiii

Configuring L2TP Services

Conventions

bold text

Indicates text that you need to enter, command names, and buttons in menu paths. Example: Enter

Example: Use the Example: ATM DXI > Interfaces >

wfsm &

dinfo

command.

PVCs

identiﬁes the PVCs button in the window that appears when you select the Interfaces option from the ATM DXI menu.

italic text

Indicates variable values in command syntax descriptions, new terms, ﬁle and directory names, and book titles.

quotation marks (“ ”) Indicate the title of a chapter or section within a book.

screen text

Indicates data that appears on the screen. Example:

Set Bay Networks Trap Monitor Filters

separator ( > ) Separates menu and option names in instructions and

internal pin-to-pin wire connections. Example: Protocols > AppleTalk identiﬁes the AppleTalk option in the Protocols menu.

Example: Pin 7 > 19 > 20

vertical line (|) Indicates that you enter only one of the parts of the

command. The vertical line separates choices. Do not type the vertical line when entering the command. Example: If the command syntax is

xiv

show at routes show at routes

, you enter either

nets

show at nets

, but not both.

300016-A Rev. 00

Acronyms

About This Guide

CHAP Challenge Handshake Authentication Protocol IP Internet Protocol ISDN Integrated Services Digital Network ISP Internet Service Provider L2TP Layer 2 Tunneling Protocol LAC L2TP access concentrator LAN local area network LCP Link Control Protocol LNS L2TP network server MPPP Multilink Point-to-Point Protocol P AP Password Authentication Protocol PPP Point-to-Point Protocol RADIUS Remote Authentication Dial-In User Service RAS remote access server RIP Routing Information Protocol SCCCN start control connection connected SCCRP start control connection reply SCCRQ start control connection request TA terminal adapter TCP/IP Transmission Control Protocol/Internet Protocol TMS tunnel management server UDP User Datagram Protocol VPN virtual private network WAN wide area network

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Configuring L2TP Services

Bay Networks Technical Publications

You can now print technical manuals and release notes free, directly from the Internet. Go to

support.baynetworks.com/library/tpubs

products for which you need documentation. 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 notes, search 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

Documentation sets and CDs are available through your local Bay Networks sales ofﬁce or account representative.

Bay Networks Customer Service

You can purchase a support contract from your Bay Networks distributor or authorized reseller, or directly from Bay Networks Services. For information about, or to purchase a Bay Networks service contract, either call your local Bay Networks ﬁeld sales ofﬁce or one of the following numbers:

. Find the Bay Networks

xvi

Region Telephone number Fax number

United States and Canada

Europe 33-4-92-96-69-66 33-4-92-96-69-96 Asia/Paciﬁc 61-2-9927-8888 61-2-9927-8899 Latin America 561-988-7661 561-988-7550

800-2LANWAN; then enter Express Routing Code (ERC) 290, when prompted, to purchase or renew a service contract

978-916-8880 (direct)

978-916-3514

Information about customer service is also available on the World Wide Web at

support.baynetworks.com

300016-A Rev. 00

How to Get Help

If you purchased a service contract for your Bay Networks product from a distributor or authorized reseller, contact the technical support staff for that distributor or reseller for assistance.

If you purchased a Bay Networks service program, call one of the following Bay Networks Technical Solutions Centers:

Technical Solutions Center Telephone number Fax number

Billerica, MA 800-2LANWAN 978-916-3514 Santa Clara, CA 800-2LANWAN 408-495-1188 Valbonne, France 33-4-92-96-69-68 33-4-92-96-69-98 Sydney, Australia 61-2-9927-8800 61-2-9927-8811 Tokyo, Japan 81-3-5402-0180 81-3-5402-0173

Bay Networks Educational Services

About This Guide

300016-A Rev. 00

Through Bay Networks Educational Services, you can attend classes and purchase CDs, videos, and computer-based training programs about Bay Networks products. Training programs can take place at your site or at a Bay Networks location. For more information about training programs, call one of the following numbers:

Region Telephone number

United States and Canada 800-2LANWAN; then enter Express Routing Code (ERC)

282 when prompted 978-916-3460 (direct)

Europe, Middle East, and Africa

Asia/Paciﬁc 61-2-9927-8822 Tokyo and Japan 81-3-5402-7041

33-4-92-96-15-83

xvii

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), which uses the e xisting physical infrastructure of a public network, such as the Internet, but offers the security and exclusivity of a private network.

This chapter contains the following information:

300016-A Rev. 00

Topic Page

L2TP Beneﬁ What Is Tunneling? 1-2 Components of an L2TP Network 1-4 L2TP Packet Encapsulation 1-8 Making a Connection Across an L2TP Network 1-9 Security in an L2TP Network 1-10 Bay Networks L2TP Implementation 1-11 Where to Go Next 1-15

ts 1-2

1-1

Configuring L2TP Services

L2TP Beneﬁts

L2TP has several advantages:

• Users and businesses can take advantage of existing network equipment and resources.

Corporations do not need to maintain and manage remote access servers and other special networking equipment for remote users. Instead, they can use their existing Internet leased connections and resources at the Internet Service Provider (ISP) network, 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 technical assistance if the user has trouble making connections.

• Remote users can place a free local call to their ISP for access to the Internet. This may not be true if they have to dial the corporate network directly.

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

• L2TP is a standards-based protocol so it provides greater interoperability with networking equipment from other vendors.

What Is Tunneling?

Tunneling is a way of forw arding traf ﬁc from remote users to a corporate netw ork through an IP 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 from an L2TP access concentrator (LAC) or remote access server (RAS) to an L2TP network server (LNS).

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

1-2

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

• 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 reestablish a tunnel, the remote user has to place a new call.

L2TP Sessions

L2TP Overview

fails, all tunnel users are disconnected.

An individual session ends when a remote user disconnects the call, but multiple sessions can run inside a single tunnel.

Packets are exchanged across an L2TP tunnel during an

L2TP session

. An L2TP session is created when an end-to-end WAN connection is established between the remote host and the LNS.

The L2TP portion of the packets sent through 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 indicates the session that the WAN packet belongs to, is negotiated between 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 ﬁelds in the header, the L2TP packet contains a

number

, which is a unique number for each L2TP call. This number matches the

call serial

call to the L2TP session.

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1-3

Configuring L2TP Services

Components of an L2TP Network

The following sections describe the components of an L2TP network. For illustrations of L2TP networks, refer to Figures 1-

Remote Host

At the remote site is the user who wants to dial in to the corporate 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 Internet.

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 dials

into a LAC, which provides a tunnel across the Internet to the corporate LNS.

• If the PC or router is an L2TP client, that is, it has built-in L2TP functionality,

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 difference between connecting an L2TP client and a nonclient is the starting point of the tunnel. For an L2TP client, the tunnel begins at the PC or router; for a non-L2TP client, the tunnel begins at the LAC. All tunnels end at the LNS.

1 and 1-2 on page 1-7.

1-4

Note:

This guide’s primary focus is on an L2TP network between a remote host that does not have built-in L2TP capabilities and uses a LA C, rather than a RAS.

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L2TP Access Concentrator (LAC)

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

Note:

In this guide, the term capabilities. The term capabilities.

When the remote user places a call to the ISP network, this call goes to the LAC. The LAC then negotiates the activation of an L2TP tunnel with the LNS. This tunnel carries data from the remote user to the corporate network.

For more information about the Bay Networks implementation of the LAC in an L2TP network, refer to “Ba

RAS

refers to a remote access server without L2TP

y Networks L2TP Implementation” on page 1-11.

Remote Access Server (RAS)

The remote access server (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

LAC

refers to a remote access server with L2TP

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

Tunnel Management Server (TMS)

At the ISP network, there needs to be a mechanism for identifying L2TP tunneled users so that the LAC can construct the L2TP tunnel. Bay Networks uses a mechanism called a tunnel management 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 termination point for L2TP tunnels and sessions.

The LNS authenticates the PPP connection request and allows the end-to-end PPP tunneled connection. The LNS may also perform user authentication with a RADIUS server to prevent unauthorized users from accessing the network; however, user authentication may also be done by the LNS itself.

An LNS can support multiple remote users, each communicating within their own L2TP session. The L2TP session is the virtual end-to-end connection over which the LAC sends data to the LNS.

The Bay Networks router is an LNS. For information about the Bay Networks LNS, refer to “Ba

y Networks L2TP Implementation” on page 1-11.

RADIUS Server

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

• Authenticating the remote users

• Assigning IP addresses to the remote users

• Providing accounting services for corporate billing The RADIUS server database centralizes the authentication function, eliminating

the need to conﬁgure each LNS with user names and passwords. It also assigns an IP address to the remote host to identify the host and ensure that it is part of its own subnet. Finally, the RADIUS server can provide accounting services for the corporate network, calculating billing charges for an L2TP session.

For information about the Bay Networks implementation of RADIUS user authentication and accounting, refer to “RADIUS User “RADIUS

1-6 300016-A Rev. 00

Accounting” on page 1-14.

Authentication” and

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

Tunnel

Data

TMS

Figure 1-1. L2TP Network Using a LAC

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

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

ISP network

Remote

host

Tunnel

RAS

Data

Frame relay

connection

Frame relay

connection

Corporate network

LNS

RADIUS

server

L2T0003A

Corporate network

LNS

L2TP

client

RADIUS

server

L2T0004A

Figure 1-2. L2TP Network Using a RAS

300016-A Rev. 00 1-7

Configuring L2TP Services

L2TP Packet Encapsulation

The PC or router at the remote site sends PPP packets to the LAC, which encapsulates these incoming packets in an L2TP packet, and sends it across an IP network through a bidirectional tunnel. A tunnel is a virtual connection between two sites, for example, an access concentrator at the ISP network and a router at the corporate network. After the LNS receives the packets, it decapsulates them and terminates the PPP connection.

igure 1-3 shows how data is encapsulated for transmission over an L2TP

network.

Remote user places a call

PPP IP

Layer 2 protocol

IP/UDP

IP DA T A

Data packet moves to the corporate network

LAC

LNS

PPP

DATA

IPL2TP

DATA

L2T0005A

Figure 1-3. Packet Encapsulation Process

1-8 300016-A Rev. 00

Making a Connection Across an L2TP Network

The following steps explain how a remote user connects across an L2TP network that includes a Bay Networks LAC, TMS, and LNS (r

1. The remote user dials a LAC at the local ISP network to establish a PPP

connection to the corporate 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 name and baynetworks.com is the domain name.

2. 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 accordingly.

efer to Figure 1-1).

L2TP Overview

3. 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.

4. After the tunnel is established, the LAC forwards the remote user’s name to

the LNS, which veriﬁes the user’ s identity with the corporate RADIUS server. If the RADIUS server recognizes the user name, it replies with an

acknowledgement 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 address of his own.

5. After the remote user is successfully authenticated, the user has an end-to-end

PPP connection to the corporate network over the Internet. The tunnel can now carry a user session during which the LAC and the LNS

exchange PPP packets.

300016-A Rev. 00 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 administrator at the corporate site can conﬁgure a RADIUS server with the names and passwords of authorized users. The server’s database centralizes the authentication function, eliminating 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 whether 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 about the Bay Networks implementation of tunnel and user authentication, refer to “T

Authentication” on page 1-14.

unnel Authentication” on page 1-12 and “RADIUS User

1-10 300016-A Rev. 00

Bay Networks L2TP Implementation

In an L2TP network, the Bay Networks router is the LNS. LNS software operates on the BLN

The Bay Networks LNS has the following characteristics:

• Each slot can act as an LNS, which means that one router can have many LNS

interfaces, each with its own address. Y ou can hav e as many LNS interf aces as there are available slots on the router.

• The LNS performs user authentication with a RADIUS server to prevent

unauthorized users from accessing 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 addresses.

, BCN®, and ASN™ platforms.

L2TP Overview

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

Figure 1-1) is a leased line operating with frame relay, PPP (including PPP

multilink), or ATM. Bay Networks recommends that you use a high-speed link, such as T1, for the leased connection.

• The LNS terminates multilink PPP 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.

Refer to Chapter 3, “Customizing L2TP Services,” for instructions on how to conﬁgure a Bay Networks router as an LNS.

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 information 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.

efer to

300016-A Rev. 00 1-11

Configuring L2TP Services

When the LAC receives a call, it forwards the domain name to the TMS. The domain name is the portion of the user’s address that speciﬁes a particular location 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.

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

does not follow a speciﬁc format. It is not related to any Domain Name System (DNS) protocol requirements.

Tunnel Authentication

For security purposes, you can enable the LNS to perform tunnel authentication. Tunnel authentication is the process of negotiating the establishment of a tunnel.

During tunnel authentication, 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 permits the LAC to establish a tunnel.

The LAC does not send the tunnel authentication password as a plain-text message. The exchange of passwords works much like the PPP Challenge Handshake Authentication Protocol (CHAP). When one side recei v es a challenge, 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, authentication is successful.

Tunnel authentication can occur in one direction, referred to as one-way authentication, or both directions, referred to as two-way authentication. If authentication is occurring in one direction, then only one side of the LAC-LNS connection tries to verify the other’ s identity. If authentication is occurring in both directions, the LAC and LNS both try to verify the other’s identity.

You can enable one-way or two-way tunnel authentication on the Bay Networks LNS. If tunnel authentication is disabled, which is the default, the LNS sends a default challenge response to the LAC during the authentication process so that the tunnel can be established. The LNS cannot send outgoing calls, so it cannot initiate tunnel authentication.

1-12 300016-A Rev. 00

L2TP Overview

During two-way tunnel authentication, the following exchange of messages takes place:

1. The LAC sends a tunnel setup message, called the start control connection

request (SCCRQ) message to the LNS. This message includes a challenge to the LNS.

2. The LNS replies with a tunnel response, a challenge response, and its own

challenge message. This is called the start control connection reply (SCCRP)

message.

3. The LAC replies with a challenge response that includes its tunnel

authentication password. This is the start control connection connected

(SCCCN) message.

4. If this same password is conﬁgured for the LNS, the LNS grants approval to

the LAC to establish a tunnel.

igure 1-4 shows two-way tunnel authentication.

ISP network

PPP connection

LAC

SCCRQ

tunnel request and challenge

tunnel response, challenge response,

SCCCN

challenge response

Corporate network

LNS

SCCRP

and LNS challenge

L2T0006A

Figure 1-4. Tunnel Authentication Control Messages

After tunnel authentication is complete, it does not need to be repeated for other calls to the same LAC.

300016-A Rev. 00 1-13

Configuring L2TP Services

RADIUS User Authentication

RADIUS user authentication is enabled by default on the Bay Networks LNS; you must conﬁgure this feature so that the LNS can validate the remote user’s identity before allowing access to the network.

The network administrator at the corporate site must conﬁgure a RADIUS server with the names and passwords of authorized users. When the LNS recei ves a call, it forwards an authentication request with the user information to the RADIUS server, which veriﬁes whether the user is authorized. If the user is permitted access to the network, the RADIUS server replies with an acknowledgement message and the appropriate address information for that user to make a connection.

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

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 server calculates billing charges for an L2TP session between the remote user and the LNS. To determine these charges, the server uses information that it receives from the LNS, such as the status of each call and the number of packets sent during the session. Using this data, the RADIUS server determines billing charges, which the network administrator can use to manage network costs.

For more information about RADIUS accounting, refer to Conﬁguring RADIUS.

1-14 300016-A Rev. 00

Assigned User Network Addresses

When conﬁguring the Bay Networks LNS, you must conﬁgure IP addresses that represent the user network for the remote hosts. These network addresses create the internal software addressing scheme for a virtual private network across the Internet.

The RADIUS server assigns the IP addresses to the remote hosts. An IP address is essential because many remote hosts may not have their own addresses. The LNS uses the address to identify the remote host and ensure that it is part of its own virtual private network. Using this address, the LNS can send data to the remote user. After the session ends, the IP address becomes available for another user.

In Site Manager conﬁguration windows, this IP address is referred to as the assigned user network. These addresses must belong to a unique subnet within the corporate network on which the LNS and the RADIUS server reside.

Be aware that if a router at the remote site dials into an ISP network, the LNS does not provide Routing Information Protocol (RIP) support. Consequently, you must conﬁgure static routes for the router for network addressing to work.

L2TP Overview

Where to Go Next

Go to one of the following chapters for more information:

• To enable L2TP on an interface, refer to Chapter 2, “Starting L2TP.”

• To customize L2TP using nondefault parameter values, refer to Chapter 3,

“Customizing L2TP Services.”

• To read parameter descriptions, refer to Appendix A, “L2TP Parameters.”

• For conﬁguration examples, refer to Appendix B, “Conﬁguration Examples.”

• For basic troubleshooting, refer to Appendix C, “Troubleshooting.”

300016-A Rev. 00 1-15

Chapter 2

Starting L2TP

The quickest way to start 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 for several parameters that do not have default values.

This chapter includes the following information:

Topic Page

Planning Considerations for an L2TP Network 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

300016-A Rev. 00 2-1

Configuring L2TP Services

Planning Considerations for an L2TP Network

This guide primarily explains 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 conﬁgure 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 passwords from your ISP. For more information about the authentication process, refer to “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:

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

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

conﬁguration.

• Conﬁgure the RADIUS server to assign IP addresses to remote users.

This address identiﬁes the remote user to the LNS during an L2TP session. If the remote user does not have a preconﬁgured address, the only way to assign addresses is by the RADIUS server. This address is also used for network communication across the subscriber network.

• Obtain the IP network addresses conﬁgured in the RADIUS server database

so you can conﬁgure them as part of the LNS assigned user network. For more information about the assigned user network, refer to “Assigned

User Network Addresses” on page 1-15.

2-2 300016-A Rev. 00

Preparing a Conﬁguration File

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

For information about the Site Manager conﬁguration tool and how to work with conﬁguration ﬁles, refer to 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 Conﬁguration Manager. The Conﬁguration Manager window

3. Choose Local File, Remote File, or Dynamic.

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

The Tools menu opens.

opens. Site Manager prompts you for the

conﬁguration ﬁle you want to open.

opens, displaying the router modules.

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

•“Ena

bling L2TP on an Unconﬁgured WAN Interface,” on page 2-4

•“Enabling L2TP on an Existing PPP Interface,” on page 2-5

•“Enabling L2TP on an Existing Frame Relay Interface,” on page 2-7

•“Enabling L2TP on an Existing ATM Interface,” on page 2-9

300016-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 Manager window, choose a WAN connector.

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

3. Choose PPP, Frame Relay, or ATM then click on OK.

4. Choose L2TP, then click on OK. The IP Conﬁguration window opens.

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

6. Set the following parameters:

• RADIUS Primary Server IP Address

• RADIUS Primary Server Password

Click on Help or refer to the parameter descriptions on page A-5.

7. Click on OK. The L2TP Tunneling Security window

8. Click on OK to accept the default values. The Assigned User Network List window

9. Set the following parameters:

• Assigned User Network

• Subnet Mask

The Add Circuit window opens.

The WAN Protocols window opens.

The Select Protocols window opens.

The L2TP Conﬁguration window opens.

opens.

opens, followed by the Assigned User Network window.

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

Click on Help or refer to the parameter descriptions on page A-10.

10.Click on OK. You return to the Assigned User Network

List window, which displays the assigned network address and the subnet mask. Following, a message window opens that reads, L2TP Configuration is completed.

(continued)

2-4 300016-A Rev. 00

Starting L2TP

Site Manager Procedure

You do this System responds

11.Click on OK. The message window closes. You return

12.Click on Done. You return to the Conﬁguration Manager

(continued)

to the Assigned User Network List window.

window.

Enabling L2TP on an Existing PPP Interface

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

Site Manager Procedure

You do this System responds

1. In the Conﬁguration Manager window, choose a WAN connector.

2. Choose Edit Circuit. The Circuit Deﬁnition window opens.

3. Choose Protocols in the top left corner of the window.

4. Choose Add/Delete. The Select Protocols window opens.

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

6. Set the following parameters:

• RADIUS Primary Server IP Address

• RADIUS Primary Server Password

The Edit Connector window opens.

The Protocols menu opens.

Click on Help or refer to the parameter descriptions on page A-5.

7. Click on OK. The L2TP Tunneling Security window

opens.

8. Click on OK. The Assigned User Network List window

opens, followed by the Assigned User Network window.

(continued)

300016-A Rev. 00 2-5

Configuring L2TP Services

Site Manager Procedure

You do this System responds

9. Set the following parameters:

• Assigned User Network

• Subnet Mask

Click on Help or refer to the parameter descriptions on page A-10.

10.Click on OK. You return to the Assigned User Network

11.Click on OK. The message window closes. You return

12.Click on Done. You return to the Circuit Deﬁnition

13.Click on Done. You return to the Conﬁguration Manager

(continued)

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

List window, which displays the assigned network address and the subnet mask. Following, a message window opens that reads, L2TP Configuration is completed.

to the Assigned User Network List window.

window.

2-6 300016-A Rev. 00

Enabling L2TP on an Existing Frame Relay Interface

T o enable L2TP on an interface with frame relay and IP already enabled, complete the following tasks:

Site Manager Procedure

You do this System responds

Starting L2TP

1. In the Conﬁguration Manager window, choose a WAN connector.

2. Choose Edit Circuit. The Frame Relay Circuit Deﬁnition

3. Choose Services. The Frame Relay Service List window

4. Choose Protocols in the top left corner of the window.

5. Choose Add/Delete. The Select Protocols window opens.

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

7. Set the following parameters:

• RADIUS Primary Server IP Address

• RADIUS Primary Server Password

Click on Help or refer to the parameter descriptions on page A-5.

8. Click on OK. The L2TP Tunneling Security window

9. Click on OK. The Assigned User Network List window

10.Set the following parameters:

• Assigned User Network

• Subnet Mask

The Edit Connector window opens.

window opens.

opens. The Protocols menu opens.

opens.

opens, followed by the Assigned User Network window.

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

Click on Help or refer to the parameter descriptions on page A-10.

(continued)

300016-A Rev. 00 2-7

Configuring L2TP Services

Site Manager Procedure

You do this System responds

11.Click on OK. You return to the Assigned User Network

12.Click on OK. The message window closes. You return

13.Click on Done. You return to the Frame Relay Service

14.Click on Done. You return to the Frame Relay Circuit

15.Click on Done. You return to the Conﬁguration Manager

(continued)

List window, which displays the assigned network address and the subnet mask for a remote user. Following, a message window opens that reads, L2TP Configuration is completed.

to the Assigned User Network List window.

List window.

Deﬁnition window.

window.

2-8 300016-A Rev. 00

Enabling L2TP on an Existing ATM Interface

T o enable L2TP on an interf ace 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 following table. If your interface uses an ATM connector, go to pa

Site Manager Procedure

You do this System responds

Starting L2TP

ge 2-10.

1. In the Conﬁguration Manager window, choose a WAN connector.

2. Choose Edit Circuit. The Circuit Deﬁnition window opens.

3. Choose Group Protocols. The Group Protocols menu opens.

4. Choose Add/Delete. The Select Protocols window opens.

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

6. Set the following parameters:

• RADIUS Primary Server IP Address

• RADIUS Primary Server Password

Click on Help or refer to the parameter descriptions on page A-5.

7. Click on OK. The L2TP Tunneling Security window

8. Click on OK. The Assigned User Network List window

9. Set the following parameters:

• Assigned User Network

• Subnet Mask

Click on Help or refer to the parameter descriptions on page A-10.

10.Click on OK. You return to the Assigned User Network

The Edit Connector window opens.

opens.

opens followed by the Assigned User IP Network window.

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

List window, which displays the assigned network address and the subnet mask. Following, a message window opens that reads, L2TP Configuration is completed.

(continued)

300016-A Rev. 00 2-9

Configuring L2TP Services

Site Manager Procedure

You do this System responds

11.Click on OK. The message window closes. You return

12.Click on Done. You return to the Circuit Deﬁnition

13.Choose File. The File menu opens.

14.Choose Exit. You return to the Conﬁguration Manager

(continued)

to the Assigned User Network List window.

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 Manager window, choose an ATM connector.

2. Choose Service Attributes. The ATM Service Records List window

3. Choose Protocols. The Protocols menu opens.

4. Choose Add/Delete. The Select Protocols window opens.

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

6. Complete steps 6 previous table.

7. Click on Done. You return to the ATM Service Records

8. Click on Done. You return to the Edit ATM Connector

9. Click on Done. You return to the Conﬁguration Manager

through 11 in the

The Edit ATM Connector window opens.

opens.

Site Manager enables L2TP.

List window.

window.

2-10 300016-A Rev. 00

Chapter 3

Customizing L2TP Services

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

This chapter includes the following information:

Topic Page

Using the MIB Object ID 3-2 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 Enabling Tunnel Authentication 3-6 Modifying the Assigned User Network List 3-7 Disabling L2TP 3-8 Deleting L2TP from a PPP Interface 3-9 Deleting L2TP from a Frame Relay Interface 3-9 Deleting L2TP from an ATM Interface 3-10

300016-A Rev. 00 3-1

Configuring L2TP Services

Using the MIB Object ID

The Technician Interface allows you to modify parameters by issuing set and

commit commands with the MIB object ID. This process is equivalent to

modifying parameters using Site Manager. For more information about using the Technician Interface to access the MIB, refer to Using Technician Interface Software.

Caution: The T echnician Interf ace does not verify parameter v alues you enter.

Entering an invalid value can corrupt you conﬁguration.

Modifying the L2TP Protocol Conﬁguration

To modify how data is transmitted across 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 parameters.

To modify the L2TP protocol conﬁguration, complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Conﬁguration Manager window, choose Protocols.

2. Choose IP. The IP menu opens.

3. Choose L2TP. The L2TP menu opens.

4. Choose L2TP Conﬁguration. The L2TP Conﬁguration List window

5. Edit any of the following parameters:

• Receive Window Size

• Retransmit Timer (seconds)

• Maximum Retransmit

• Hello Timer (seconds)

• Ack Timeout (milliseconds)

Click on Help or refer to the parameter descriptions beginning on page A-3.

6. Click on Done. You return to the Conﬁguration Manager

3-2 300016-A Rev. 00

The Protocols menu opens.

opens.

window.

Modifying RADIUS Server Information

If you change the address of the RADIUS server that you are using to authenticate 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, refer to “RADIUS Server” on page 1-6.

To modify the address of the RADIUS server, complete the following tasks:

Site Manager Procedure

You do this System responds

Customizing L2TP Services

1. In the Conﬁguration Manager window, choose Protocols.

2. Choose IP. The IP menu opens.

3. Choose L2TP. The L2TP menu opens.

4. Choose L2TP Conﬁguration. The L2TP Conﬁguration List window

5. Set the following parameters:

• RADIUS Primary Server IP Address

• RADIUS Primary Server Password

• RADIUS Client IP Address

Click on Help or refer to the parameter descriptions beginning on page A-5.

6. Click on Done. You return to the Conﬁguration Manager

The Protocols menu opens.

opens.

window.

300016-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. Refer to Conﬁguring and Managing Routers with Site Manager for more details 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 Manager window, choose Protocols.

2. Choose IP. The IP menu opens.

3. Choose L2TP. The L2TP menu opens.

4. Choose L2TP Conﬁguration. The L2TP Conﬁguration List window

5. Set the LNS System Name parameter. Click on Help or refer to the parameter description on page A-5.

6. Click on Done. You return to the Conﬁguration Manager

The Protocols menu opens.

opens.

window.

3-4 300016-A Rev. 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, refer to “L2TP Sessions” on page 1-3. To change the maximum number of L2TP sessions supported by the LNS,

complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Conﬁguration Manager window, choose Protocols.

2. Choose IP. The IP menu opens.

3. Choose L2TP. The L2TP menu opens.

4. Choose L2TP Conﬁguration. The L2TP Conﬁguration List window

5. Set the Max L2TP Sessions parameter. Click on Help or refer to the parameter description on page A-3.

6. Click on Done. You return to the Conﬁguration Manager

The Protocols menu opens.

opens.

window.

300016-A Rev. 00 3-5

Configuring L2TP Services

Enabling T unnel Authentication

To prevent unauthorized 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.

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

authentication, do not enable tunnel authentication.

For more information about tunnel authentication, refer to “Tunnel Authentication,” on page 1-12.

To enable tunnel authentication, complete the following tasks:

Site Manager Procedure

You do this System responds

1. In the Conﬁguration Manager window, choose Protocols.

2. Choose IP. The IP menu opens.

3. Choose L2TP. The L2TP menu opens.

4. Choose Tunnel Authentication. The L2TP Tunneling Security window

5. Set the following parameters:

• Enable T unnel Authentication

• Tunnel Authentication Password

Click on Help or refer to the parameter descriptions beginning on page A-8.

6. Click on Done. You return to the Conﬁguration Manager

The Protocols menu opens.

opens.

window.

3-6 300016-A Rev. 00

Modifying the Assigned User Network List

The Assigned User Network List window lists the valid user network addresses. These IP addresses complete the virtual private network addressing scheme between the corporate and remote sites. The addresses in this list must be part of a unique subnet that the RADIUS server uses to assign IP addresses to the remote user.

For more information about assigned user networks, refer to “Assigned User Network Addresses” on page 1-15.

To add an address to the list, complete the following tasks:

Site Manager Procedure

You do this System responds

Customizing L2TP Services

1. In the Conﬁguration Manager window, choose Protocols.

2. Choose IP. The IP menu opens.

3. Choose L2TP. The L2TP menu opens.

4. Choose Assigned User Network. The Assigned User Network List window

5. Click on Add. The Assigned User Network window

6. Set the following parameters:

• Assigned User Network

• Subnet Mask

Click on Help or refer to the parameter descriptions beginning on page A-10.

7. Click on OK. You return to the Assigned User Network

8. Click on Done. You return to the Conﬁguration Manager

The Protocols menu opens.

opens.

List window . The ne w address appears in the list.

window.

300016-A Rev. 00 3-7

Configuring L2TP Services

To delete an address from the list, complete the following tasks:

You do this System responds

Site Manager Procedure

1. In the Conﬁguration Manager window, choose Protocols.

2. Choose IP. The IP menu opens.

3. Choose L2TP. The L2TP menu opens.

4. Choose Assigned User Network. The Assigned User Network List window

5. Select an address in the list and click on Delete.

6. Click on Done. You return to the Conﬁguration Manager

Disabling L2TP

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

You do this System responds

1. In the Conﬁguration Manager window, choose Protocols.

2. Choose IP. The IP menu opens.

3. Choose L2TP. The L2TP menu opens.

4. Choose L2TP Conﬁguration. The L2TP Conﬁguration List window

5. Choose the slot with the L2TP interface you want to disable.

6. Set the Enable L2TP parameter to Disable. Click on Help or refer to the parameter description on page A-3.

7. Click on Done. You return to the Conﬁguration Manager

The Protocols menu opens.

opens. Site Manager removes the address from

the list.

window.

Site Manager Procedure

The Protocols menu opens.

opens. Site Manager selects the slot entry in the

scroll box. Site Manager disables L2TP for the slot.

window.

3-8 300016-A Rev. 00

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

Customizing L2TP Services

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

2. Choose Edit Circuit. The Circuit Deﬁnition window opens.

3. Choose Protocols. The Protocols menu opens.

4. Choose Add/Delete. The Select Protocols window opens.

5. Click on L2TP. Site Manager deselects L2TP.

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

7. Click on Done. You return to the Conﬁguration Manager

The Edit Connector window opens.

window.

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 Manager window, click on a WAN connector conﬁgured with L2TP.

2. Choose Edit Circuit. The Frame Relay Circuit Deﬁnition

3. Choose Services. The Frame Relay Service List window

4. Choose Protocols in the top left corner of the window.

5. Choose Add/Delete. The Select Protocols window opens.

The Edit Connector window opens.

window opens.

opens. The Protocols menu opens.

(continued)

300016-A Rev. 00 3-9

Configuring L2TP Services

Site Manager Procedure

You do this System responds

6. Click on L2TP. Site Manager deselects L2TP.

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

8. Click on Done. You return to the Frame Relay Circuit

9. Click on Done. You return to the Conﬁguration Manager

Deleting L2TP from an ATM Interface

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

Site Manager Procedure

You do this System responds

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

2. Choose Edit Circuit. The Circuit Deﬁnition window opens.

3. Choose Group Protocols. The Group Protocols menu opens.

4. Choose Add/Delete. The Select Protocols window opens.

5. Click on L2TP. Site Manager deselects L2TP.

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

7. Choose File. The File menu opens.

8. Choose Exit. You return to the Conﬁguration Manager

(continued)

List window.

Deﬁnition window.

window.

The Edit Connector window opens.

window.

3-10 300016-A Rev. 00

Customizing L2TP Services

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

Site Manager Procedure

You do this System responds

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

2. Choose Service Attributes. The ATM Service Records List window

3. Choose Protocols in the top left corner of the window.

4. Choose Add/Delete. The Select Protocols window opens.

5. Click on L2TP. Site Manager deselects L2TP.

6. Click on OK. You return to the ATM Service Records

7. Click on Done. You return to the Edit ATM Connector

8. Click on Done. You return to the Conﬁguration Manager

The Edit ATM Connector window opens.

opens. The Protocols menu opens.

List window.

window.

300016-A Rev. 00 3-11

Appendix A

L2TP Parameters

This appendix contains the parameter descriptions for L2TP services. For information about the IP parameters that you set when enabling L2TP, refer to Conﬁguring IP Services.

This appendix contains the following information:

Topic Page

L2TP Conﬁguration Parameters A-2 L2TP Tunnel Security Parameters A-7 Assigned User Network Parameters A-9

300016-A Rev. 00 A-1

Configuring L2TP Services

L2TP Conﬁguration Parameters

The L2TP Conﬁguration List window (Figure A-1) contains parameters that deﬁne how L2TP sends and receives data.

Figure A-1. L2TP Conﬁguration List Window

The parameter descriptions follow.

A-2 300016-A Rev. 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: Site Manager automatically enables this parameter when you select L2TP as a

protocol. Accept the def ault, Enable, 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: Enter the maximum number of L2TP session that you want 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 packets 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 value.

MIB Object ID: 1.3.6.1.4.1.18.3.5.23.2.1.6

300016-A Rev. 00 A-3

Configuring L2TP Services

Parameter: Retransmit Timer (seconds)

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 the maximum number of seconds that can elapse without 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 default.

MIB Object ID: 1.3.6.1.4.1.18.3.5.23.2.1.9

A-4 300016-A Rev. 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 acknowledgment to the LA C that it recei ved an L2TP control 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, set 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 Server 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

300016-A Rev. 00 A-5

Configuring L2TP Services

Parameter: RADIUS Primary Server 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 password.

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 entire router .

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

Site Manager automatically supplies the address.

MIB Object ID: 1.3.6.1.4.1.18.3.5.22.1.1.5

A-6 300016-A Rev. 00

L2TP Tunnel Security Parameters

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

L2TP Parameters

Figure A-2. L2TP Tunnel Security List Window

The parameter descriptions follow.

300016-A Rev. 00 A-7

Configuring L2TP Services

Parameter: Enable Tunnel A uthentication

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

Default: Disable

Options: Enable

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

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

Otherwise, accept the default, Disable. T unnel authentication provides a le v el of network security to protect the corporate network from unauthorized users.

MIB Object ID: 1.3.6.1.4.1.18.3.5.23.1.1.2

Parameter: T unnel A uthentication Password

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

Default: None

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

Function: Identiﬁes the LNS to the LAC if the devices are using tunnel authentication. 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

| Disable

A-8 300016-A Rev. 00

Assigned User Network Parameters

The Assigned User Network List window (Figure A-3) contains the list of IP network addresses assigned to remote users. These addresses create the unique virtual subnet.

L2TP Parameters

Figure A-3. Assigned User Network List Window

When you add a new entry to the assigned user network list, Site Manager displays the Assigned User Network Window (F

Figure A-4. Assigned User Network Window

300016-A Rev. 00 A-9

igure A-4).

Configuring L2TP Services

The parameter descriptions follow.

Parameter: Assigned User Network

Path: Conﬁguration Manager > Protocols > IP > L2TP > Assigned User Network

Default: None

Options: Any unique IP network address that is valid for the user network

Function: Identiﬁes the IP address that deﬁnes the network to which the remote user

belongs.

Instructions: Enter a unique IP network address that belongs to a unique subnet within the

corporate network. This address must be the same addresses as entered in the RADIUS server database.

MIB Object ID: Not Applicable

Parameter: Subnet Mask

Path: Conﬁguration Manager > Protocols > IP > L2TP > Assigned User Network

Default: None

Options: A 32-bit IP subnet mask

Function: Speciﬁes the network and subnet portion of the assigned user network.

Site Manager automatically calculates 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. If the assigned user network is

192.32.16.0, you can have 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

A-10 300016-A Rev. 00

Appendix B

Conﬁguration Examples

This appendix provides two examples of L2TP network conﬁgurations. It includes only those parameters that require changes from their default settings for proper conﬁguration. For instructions on modifying parameters, refer to Chapter 3, “Customizing L2TP Services.”

This appendix assumes that you are familiar with L2TP conﬁguration procedures. For information about setting up an interface on the router , refer to 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.

• Assigned user network is the unique virtual private subnet.

• Frame relay is the WAN protocol for the connection between the ISP network and the corporate network.

300016-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 relay

Tunnel

Corporate network

LNS

192.32.16.55

192.32.40.0

Assigned user network

Assigned user network in the RADIUS server database

192.32.40.1 jsmart@baynetworks.com

192.32.40.2 mmark@baynetworks.com

.17

RADIUS server

192.32.26.6 bay_private

Router

.26.0

L2T0007A

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 capabilities.

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 adapter (TA).

The user names at the PCs are jsmart@baynetworks.com and mmark@baynetworks.com.

B-2 300016-A Rev. 00

Conﬁguring the LACs and the TMS

The LACs in this network are Model 5399 Remote Access Concentrators. Both devices have L2TP modules installed. Refer to Model 5399 Remote Access Concentrator documentation 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:

1. Choose one of the WAN ports for the slot you want as the LNS.

Configuration Examples

2. From the WAN Protocols menu, choose Frame Relay.

3. From the Select Protocols menu, choose IP and L2TP.

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

Table B-1. IP Address Parameter

Parameter Name Value

IP Address 192.32.16.55

5. In the L2TP Conﬁguration List window, enter the RADIUS server

information.

Table B-2. RADIUS Server Parameters

Parameter Name Value

RADIUS Primary Server IP Address 192.32.26.6 RADIUS Primary Server Password bay_private

300016-A Rev. 00 B-3

Configuring L2TP Services

6. In the L2TP Tunneling Security window, enable tunnel authentication.

Table B-3. Tunnel Authentication Parameters

Parameter Name Value

Enable Tunnel Authentication Enable Tunnel Authentication Password LAC1

7. In the Assigned User Network window, create the necessary entries.

Table B-4. Assigned User Network Parameters

Parameter Name Value

Assigned User Network 192.32.40.0 Subnet Mask 255.255.255.0

During the L2TP session, the IP network addresses are assigned as follows: jsmart@baynetworks.com: 192.32.40.1

mmark@baynetworks.com: 192.32.40.2 These addresses are stored in the RADIUS server database.

Data Path Through the Network

After all components of the network are set up, jsmart can place a call to the local ISP. The LAC that receives 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 negotiates 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 include 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 300016-A Rev. 00

Configuration Examples

Example 2: Remote Router Calling the Corporate Network

Figure B-2 shows a network with two AN routers at the remote site. The routers

are using dial-on-demand service for dial-up connections. In this network, note the following:

• PPP is the WAN protocol for the connection between the ISP network and the corporate network.

• The IP network addresses are assigned as follows: jsmart@bay.com: 192.32.40.1

mmark@bay.com: 192.32.40.2

The conﬁguration for the LNS in this network is the same as in Example 1; however, you need to modify the conﬁguration of the AN remote routers as described in the following sections.

For information about dial-on-demand, refer to Conﬁguring Dial Services. For information about PPP, refer to Conﬁguring PPP Services.

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

Tunnel

Corporate network

LNS

PPP

192.32.16.55 .17

192.32.40.0

Assigned user network

Assigned user network in the RADIUS server database

192.32.40.1 jsmart@bay.com

192.32.40.2 mmark@bay.com

Router

.26.0

RADIUS server

192.32.26.6 bay_private

L2T0008A

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

300016-A Rev. 00 B-5

Configuring L2TP Services

Dial-on-Demand Circuit Conﬁguration

Modify the dial-on-demand circuit conﬁguration as follows:

1. In the Conﬁguration Manager window , choose Dialup > Demand Circuits

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

2. Disable outbound authentication.

Table B-5. PPP Demand Circuit Parameters

Parameter Name Value

Outbound Authentication Disable CHAP Local Name jsmart@bay.com

PPP Interface Conﬁguration

Modify the PPP interface conﬁguration as follows:

1. In the Conﬁguration Manager window, choose Protocols > PPP >

Interfaces to access the PPP Interface List window.

2. Click on Lines to access the PPP Line List window.

3. Enable RFC 1661 compliance, as follows:

Table B-6. PPP Line List Parameter

Parameter Name Value

RFC1661 Compliance Enable

Adjacent Host Conﬁguration

After you set up the router’s dial-on-demand conﬁguration, you are prompted for an adjacent host address. Enter the assigned user network address from the LNS as the adjacent host address.

The adjacent host address is the user network address assigned by the LNS. In this example, it would be 192.32.40.254.

B-6 300016-A Rev. 00

Appendix C

Troubleshooting

T o monitor your L2TP netw ork and solve problems that may occur, ﬁrst check the event log ﬁle for any messages recorded by the LNS. For information about viewing and reading event messages, refer to Event Messages for Routers and Conﬁguring and Managing Routers with Site Manager.

able C-1 provides troubleshooting solutions for common problems with your

L2TP network.

Table C-1. Common L2TP Network Problems and Solutions

Problem What to Do

L2TP tunnel did not initiate. Check whether you enabled tunnel authentication f or

the LNS on that slot. If authentication is enabled, make sure that the

authentication password is the same for the LA C and the LNS.

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

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

300016-A Rev. 00 C-1

Check the address conﬁgured in the RADIUS server database and make sure that the address is part of the virtual private subnet as conﬁgured in the Assigned User Network List.

(continued)

Configuring L2TP Services

Table C-1. Common L2TP Network Problems and Solutions

Problem What to Do

L2TP session is not active. The LNS failed to negotiate 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 following 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, 12.00, and 12.10, set the PPP parameter RFC 1661 Compliance Mode to Enable.

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

A router at the remote site cannot tunnel into the corporate network.

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

(continued)

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.

C-2 300016-A Rev. 00

Index

Ack Timeout (seconds) parameter, A-5 addresses, assigning IP network, 3-7 assigned user network list, modifying, 3-7 Assigned User Network parameter, A-10

Bay Networks LNS. See LNS

conﬁguration examples, B-1 conﬁguration ﬁle, requirements, 2-3 customer support

programs, xvi Technical Solutions Centers, xvii

deleting L2TP

from ATM, 3-10, 3-11 from frame relay, 3-9

from PPP, 3-9 disabling L2TP, 3-8 domain name, description, 1-12

Enable L2TP parameter, A-3 Enable Tunnel Authentication parameter, A-8

Hello Timer (seconds) parameter, A-4

L2TP

customizing conﬁguration, 3-1 data transmission across network, 1-9 deleting, ATM interface, 3-10, 3-11 deleting, frame relay interface, 3-9 deleting, PPP interface, 3-9 description, 1-1 disabling, 3-8 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 network server. See LNS LAC

conﬁguration example, B-3

description, 1-5

tunnel authentication, security, 1-10, 1-12 Layer 2 Tunneling Protocol. See L2TP LNS

Bay Networks implementation, 1-11

changing RADIUS server address, 3-3

changing system name, 3-4

conﬁguration example, B-3

conﬁguring router as, 2-3

customizing parameters, 3-1

description, 1-6

enabling tunnel authentication, 3-6

L2TP security, 1-10

modifying protocol conﬁguration, 3-2

operating with LACs, 1-11

300016-A Rev. 00 Index-1

LNS System Name parameter, A-5 LNS system name, changing, 3-4

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

TMS, description, 1-5, 1-11 troubleshooting network problems, C-1 Tunnel Authentication Password parameter, A-8 tunnel authentication, enabling, 3-6 tunnel management server. See TMS tunnel, description, 1-8

packet encapsulation, L2TP, 1-8 parameters

customizing, 3-1 descriptions, A-1

Avaya LT2P User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Contents

Figures

Tables

About This Guide

Before Y ou Begin

Conventions

Acronyms

Bay Networks Technical Publications

Bay Networks Customer Service

How to Get Help

Bay Networks Educational Services

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

Assigned User Network Addresses

Where to Go Next

Planning Considerations for an L2TP Network

Tunnel Authentication Passwords

RADIUS Server Information

Enabling L2TP on an Existing PPP Interface

Enabling L2TP on an Existing ATM Interface

Using the MIB Object ID

Modifying RADIUS Server Information

Changing the LNS System Name

Modifying the Number of L2TP Sessions Permitted

Enabling T unnel Authentication

Modifying the Assigned User Network List

Disabling L2TP

Deleting L2TP from a PPP Interface

Deleting L2TP from a Frame Relay Interface

Deleting L2TP from an ATM Interface

L2TP Tunnel Security Parameters

Assigned User Network Parameters

Data Path Through the Network

Index