L2TP Overview

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 server determines billing charges, which the network administrator can use to manage 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.

The L2TP IP interface address is internal to the LNS. When communicating with the remote user, the LNS associates 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 RADIUS-assigned IP address do not have to be in the same subnet.

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Nortel Networks manual Radius Accounting, L2TP IP Interface Addresses

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.