What is L2F (Layer 2 Forwarding)? | How Does It Work?

L2F (Layer 2 Forwarding) is a secure VPN protocol by Cisco. It creates private networks for fast access to networks. This helps with remote access to company networks.

What is the L2F Protocol in a Secure Communication Network?

Cisco developed the PPTP protocol. Also, they created the L2F technology. The purpose of this tech is to tunnel traffic from remote users to the central corporate network.

The main difference between L2F and PPTP is in the tunneling process. Also, it works directly in other network environments like Frame Relay or ATM.

The L2F VPN uses PPP for remote authentication. It also employs secure methods for data transfer:

• TACACS + (Terminal Access Controller Access Control System)
• RADIUS (Remote Authentication Dial-In User Service)

Also, L2F tunnels have many connections that are different from those of PPTP tunnels. For example, the ISP and the company check two users before making a tunnel.

So, it checks with the gateway for two-user authentication. Then, a tunnel forms between local and remote networks.

L2F is in the data link layer of the OSI model. So, it supports IPX or NetBEUI, not IP, as PPTP does.

In short, Cisco’s protocol isn’t limited to just IP; it works with others. It also works with VDU, a virtual dial-up service.

History of L2F Protocol

The history of Layer 2 Forwarding, L2F, started in the late 1990s. It offered a secure remote access method. In simpler terms, it improved data transmission.

That’s why Cisco created L2F in 1996. This protocol enabled secure access to company networks. As a result, it gained attention.

After a while, Cisco updated L2F. They made it work faster, keep data safe, and work with more things.

People might not use L2F, but it started the idea for this special Internet connection.

L2F Features

Leading the development of VPN technology, the main features of L2F are:

1. Tunneling and Security

The tunneling feature helps transfer data traffic on the network safely. This method provides encryption when you try to access a remote network through the Internet.

2. Authentication

Apart from confirming the user’s identity, it also encrypts their other info. This way ensures the network’s security and grants users access rights.

3. Data Encryption

L2F makes data safe and stops strangers from getting in. So, it keeps user info secure.

4. Multi-Network Support

Ethernet works with Frame Relay and other protocols, plus it’s safe.

5. Secure Remote Access

When you want to connect to faraway networks, choose the safest route. This method ensures the secure linking of your company networks from various places.

6. Protocol Compatible

It works smoothly in network environments. It plays well with other protocols, especially in big organizations.

7. High Performance

The L2F protocol swiftly sends secure data between networks. This approach is a popular choice for excellent performance.

How Does the L2F Protocol Work?

With the Layer 2 Forwarding protocol, you can create networks based on VPNs. However, it would be best if you examined how it works by reviewing some steps involved.

1. Tunneling Process

L2F’s primary goal is secure data transmission. It creates a tunneling channel first. Then, it connects to a remote VPN server for protection.

2. Client and Server Communication

A person connects to a remote server using L2F client software. Later, the server confirms the person’s identity for safety.

3. Tunneling

The VPN server checks the user and creates a safe pathway. Then, it encrypts data for security while sending it.

4. Data Transmission

After making the tunnel, it encodes the info to the server. So, it creates a safe space between the local and remote networks.

5. Completion of the Connection

The tunnel closes when the user wants to end the connection with the server. After that, it safely removes the connected person from the network and protects them.

What Are the Authentication Protocols Used in VPN Connection?

• PAP Protocol

Once connected, the client sends login details and verifies user identity. Then, it confirms or denies the connection request based on that info.

• CHAP Protocol

This process regularly sends a message to the server to ensure it is you. In simpler terms, it uses special packets to talk securely between the server and your device. Both sides check your username and password for safety. This way, they make sure it’s you connecting or disconnecting from the network.

How to Create a Tunnel?

An L2F tunnel includes the following steps;

1. The remote user starts a PPP connection through an ISP. They use a PSTN or ISDN gateway for this connection.
2. After the NAS accepts the link, the PPP connection is established. Then, the ISP starts using a unique code to check if everything is secure.
3. The system uses only the username to establish a CHAP or PAP connection.
4. After assigning a Multiplex ID (MID), it sends a connection packet to the destination of VDU.
5. After establishing the connection, a virtual tunnel for SLIP or PPP is created. As a result, it allows data to flow in both directions.
6. In this tunnel way, devices that establish a connection using CHAP will periodically verify the link.

L2F Usage Areas

• Corporate Remote Access

People use it to work from far away, like connecting to their company’s PC system. For instance, employees who work from home or staff who are traveling can easily create a remote office with this system.

• Intercompany Connections

Partnerships between companies need knowledge sharing. So, you can create a secure connection with L2F to link networks.

• Telecommunications Sector

Telecom companies use L2F to give customers broadband Internet or phone service.

• Health Service

In healthcare, they often use L2F to send patient information safely. This makes it more secure to share sensitive patient data.

• Educational Institutions

The primary reason schools use L2F is for online learning. This way, students can connect to the school’s computer system from afar and get the things they need.

• Government and Public Institutions

The big reason for using L2F in schools is to learn from far away. This way, students can connect to their school’s computer system from home and get what they need.

• Industrial Control and Automation

You can use it to make a safe network between factories or automation systems so they can manage their work better.

Layer 2 Forwarding Package Structure