Nortel Networks manual Table C-1 Common L2TP Network Problems and Solutions

Page 78

Configuring L2TP Services

Table C-1.

Common L2TP Network Problems and Solutions (continued)

 

 

 

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 and later

 

 

set the PPP parameter RFC1661 Compliance to

 

 

Enable.

 

 

You can also check the session statistics, which are

 

 

automatically enabled on the LNS.

 

 

Bay Networks router at the remote

Check the IP address assigned by the RADIUS

site cannot tunnel into the

server. There may be a mismatch between the

corporate network.

address of the remote router dialing in to the LAC

 

 

and the address that the RADIUS server assigns.

 

 

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

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Contents Configuring L2TP Services Copyright 1998 Bay Networks, Inc Bay Networks, Inc. Software License Agreement Rev Contents Chapter Starting L2TP Appendix B Configuration Examples Page Figures Page Tables Page Preface Before You BeginText Conventions Italic textAcronyms How to Get Help Bay Networks Technical PublicationsChapter L2TP Overview TopicWhat Is Tunneling? L2TP BenefitsL2TP Sessions Components of an L2TP Network Remote HostL2TP Access Concentrator LAC Remote Access Server RASTunnel Management Server TMS L2TP Network Server LNS Radius ServerL2TP Network Using a LAC Examples of L2TP NetworksL2TP Packet Encapsulation Packet Encapsulation ProcessMaking a Connection Across an L2TP Network Security in an L2TP Network Bay Networks L2TP Implementation Tunnel Authentication Tunnel ManagementShows tunnel authentication Radius User Authentication Radius Accounting L2TP IP Interface AddressesRemote Router Configuration Remote Router Dialing the LNSWhere to Go Next If you want to Go toPage Chapter Starting L2TP Tunnel Authentication Passwords Planning Considerations for an L2TP NetworkRadius Server Information Tools Choose Configuration Manager Preparing a Configuration FileSite Manager Procedure You do this System responds Choose Local File , Remote File , orEnabling L2TP on an Unconfigured WAN Interface Subnet MaskEnabling L2TP on an Existing PPP Interface Choose Edit CircuitChoose Add/Delete Configuring L2TP Services Enabling L2TP on an Existing Frame Relay Interface Configuration is completed You do this System responds Site Manager ProcedureEnabling L2TP on an Existing ATM Interface Choose Group ProtocolsChoose Service Attributes Choose ProtocolsChapter Customizing L2TP Services Modifying the L2TP Protocol Configuration Choose L2TP ConfigurationModifying Radius Server Information Radius Server onChanging the LNS System Name Modifying the Number of L2TP Sessions Permitted Keeping the Remote User’s Domain Name Set the Remove Domain NameChanging the Domain Name Delimiter Set the Domain Name DelimiterEnabling Tunnel Authentication Choose Tunnel AuthenticationModifying L2TP IP Interface Addresses Choose L2TP IP InterfaceDisabling RIP Disabling L2TPCustomizing L2TP Services Deleting L2TP from a PPP InterfaceDeleting L2TP from a Frame Relay Interface Deleting L2TP from an ATM Interface Site Manager Procedure Appendix a L2TP Parameters TopicL2TP Configuration Parameters Figure A-1. L2TP Configuration List WindowParameter Enable L2TP Parameter Max L2TP SessionsParameter Receive Window Size Parameter Retransmit Timer seconds Parameter Hello Timer secondsParameter Maximum Retransmit Parameter Ack Timeout milliseconds Parameter LNS System NameParameter Radius Primary Server IP Address Parameter Radius Primary Server Password Parameter Radius Client IP AddressParameter Tunnel Flow Control Parameter Remove Domain Name Parameter Domain Name DelimiterL2TP Tunnel Security Parameters Figure A-2. L2TP Tunnel Security List WindowParameter Enable Tunnel Authentication Parameter Tunnel Authentication PasswordL2TP IP Interface Parameters Figure A-3. L2TP IP Interface List WindowParameter L2TP IP Interface Address Parameter Subnet MaskParameter RIP Enable Appendix B Configuration Examples Example 1 Remote PC Calling the Corporate NetworkConfiguring the Remote Hosts Figure B-1. L2TP Network with PCs at the Remote SiteDomain name baynetworks.com Configuring the LACs and the TMSConfiguring the LNS Parameter Name Value IP Address 192.32.16.55Data Path Through the Network L2TP IP Interface window, enter the L2TP IP addressExample 2 Remote Router Calling the Corporate Network Figure B-2. L2TP Network with Routers at the Remote SiteConfiguring the Dial-on-Demand Circuit Configuring the PPP InterfaceParameter Name Value RFC1661 Compliance Enable Appendix C Troubleshooting Problem What to DoTable C-1 Common L2TP Network Problems and Solutions Index L2TPIndex-2

L2TP specifications

Nortel Networks L2TP, or Layer 2 Tunneling Protocol, is a widely recognized networking protocol that enables the tunneling of data over various networks. Initially developed as an extension of the Point-to-Point Tunneling Protocol (PPTP), L2TP integrates components from both PPTP and Layer 2 Forwarding (L2F). Nortel Networks played a significant role in the development and implementation of L2TP, making it a prominent choice for service providers and enterprise networks seeking secure and efficient connectivity.

One of the primary features of L2TP is its ability to encapsulate data packets, allowing the transport of PPP (Point-to-Point Protocol) frames without necessitating the traditional point-to-point connections. This means L2TP can operate across different networks, facilitating remote access connections and VPNs (Virtual Private Networks). As a result, organizations can achieve greater flexibility in managing their communications infrastructure.

Another key characteristic of L2TP is its support for both IPv4 and IPv6, ensuring compatibility with current and future networking environments. L2TP operates at the link layer of the OSI model, which means it functions between the data link and network layers, making it versatile for various applications. By using UDP (User Datagram Protocol) as a transport protocol, L2TP ensures efficient data transmission while maintaining lower latencies.

Security is a critical aspect of L2TP. While L2TP itself does not provide encryption, it is often paired with IPSec (Internet Protocol Security) for enhanced security protocols. This combination offers both tunneling and encryption, creating a secure framework for transmitting sensitive information across potentially insecure networks, such as the Internet.

L2TP also features various authentication methods, allowing for robust access control. It supports various schemes like PAP (Password Authentication Protocol) and CHAP (Challenge Handshake Authentication Protocol), giving network administrators a range of options to ensure the legitimacy of users accessing the network.

In summary, Nortel Networks L2TP is a powerful tunneling protocol known for its flexibility, compatibility, and security features. Its ability to encapsulate data for efficient transport makes it ideal for remote access and VPN applications. As organizations continue to demand secure, seamless connectivity, L2TP remains a resilient choice within the shifting landscape of networking technologies.
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