{"id":321,"date":"2023-04-11T08:25:37","date_gmt":"2023-04-11T08:25:37","guid":{"rendered":"https:\/\/dataprot.net\/?p=321"},"modified":"2023-05-06T06:04:24","modified_gmt":"2023-05-06T06:04:24","slug":"what-is-l2tp","status":"publish","type":"post","link":"https:\/\/dataprot.net\/guides\/what-is-l2tp\/","title":{"rendered":"What Is the L2TP VPN Protocol?"},"content":{"rendered":"\n

An unspoken techie rule goes: Out with the old, in with the new. We\u2019re constantly being offered newer and improved software solutions designed to be safer and better suit our needs. However, some pieces of software keep defying the ravages of time, and L2TP is one of them.<\/p>\n\n\n\n

L2TP or Layer 2 Tunneling Protocol is a VPN protocol<\/a> that\u2019s been around since 2000 and is still very much available. Since then, VPN technology has made great strides in providing faster and more secure protocols. However, L2TP still has a couple of aces up its sleeve, which we\u2019ll discuss in this article.<\/p>\n\n\n\n

The Short History of the L2TP protocol<\/h2>\n\n\n\n

L2TP was built upon Microsoft\u2019s Point-to-Point Tunneling Protocol (PTPP), and it\u2019s employed by internet service providers (ISPs) to enable VPN connections.<\/p>\n\n\n\n

As a series of digital communication procedures, L2TP is only used to offer tunneling capabilities. It gathers user data via private transportation and sends it over public networks. In combination with IPSec, a Layer 3 protection protocol, L2TP provides confidentiality and encryption for VPN functionality.<\/p>\n\n\n\n

L2TP was developed by Microsoft and Cisco with the goal to use it as a replacement for the PTPP. It was published in 1999\/2000 as the RFC 2661 protocol.<\/p>\n\n\n\n

The technology behind this protocol relied on two older tunneling protocols used for establishing a point-to-point connection. The first protocol was Microsoft\u2019s Point-to-Point Tunneling Protocol (PPTP), while the second was Cisco\u2019s Layer 2 Forwarding Protocol (L2F).<\/p>\n\n\n\n

In 2005, a new protocol version, L2TPv3, provided enhanced encapsulation, more security options, and carried data links in new ways.<\/p>\n\n\n\n

\"vpn<\/figure>\n\n\n\n

How It Works<\/h2>\n\n\n\n

L2TP allows for tunneling L2 traffic via an IP network or L3 network. L2 and L3 here refer to the second and third levels in a seven-layer OSI, a telecommunication and computer standardization model. L2 is the Data Link layer, while L3 is the Network Layer. L3 works atop L2, which runs over L1, the Physical Layer.<\/p>\n\n\n\n

It all starts when L2TP connection is established between the protocol\u2019s two endpoints – the L2TP Access Concentrator (LAC) and the L2TP Network Server (LNS). Once these two are connected and the L2TP tunnel is created, a PPP link layer is enabled, encapsulated, and sent over the internet.<\/p>\n\n\n\n

After this, the PPP connection is established by the end-user with the ISP. When the LAC accepts this connection, the PPP link is up and running. A free slot within the network is assigned, and the request moves on to the LNS.<\/p>\n\n\n\n

When this connection is fully authorized and active, a virtual PPP interface appears and the passage of link frames through the tunnel can begin. The LNS accepts the frames, removes their encapsulation, and processes them further as regular frames.<\/p>\n\n\n\n

\"l2tp<\/figure>\n\n\n\n

Components of an L2TP Configuration<\/h3>\n\n\n\n

There are two primary components of L2TP: a tunnel and a session. The tunnel allows secure transport between two L2TP control connection endpoints. Through it, you can only send and receive control packets.<\/p>\n\n\n\n

The other significant component – the session – is responsible for carrying user data through the tunnel. One tunnel can contain more than one session. In that case, session identifier numbers keep user data separate.<\/p>\n\n\n\n

L2TP\/IPSec Combination for Enhanced Security<\/h3>\n\n\n\n

L2TP by itself uses no encryption or authentication methods despite being an evolutionary step forward from PPTP. L2TP\u2019s primary purpose is to establish a VPN tunnel<\/a>. For encryption, it has to be bundled with other technologies, such as IPSec.<\/p>\n\n\n\n

IPSec is a strong security protocol that employs a robust AES encryption cipher. This protocol also relies on double encapsulation as an additional method of data protection.<\/p>\n\n\n\n

As for IPSec\u2019s level of security, the Snowden leaks have revealed that the NSA was trying to crack or weaken this protocol as part of its Bullrun program. While none of these allegations have been proved to be accurate, it is something every VPN user should take into account when thinking about their data security and choosing their VPN protocol.<\/p>\n\n\n\n

The L2TP\/IPSec VPN connection starts with the IPSec security association (SA) negotiation that usually goes through Internet key exchange (IKE) and UDP port 500. This connection needs a shared password, an X.509 international telecommunication certificate, or a public key.<\/p>\n\n\n\n

Afterward, this protocol creates an Encapsulated Security Payload (ESP) that allows devices on both sides to determine where the data comes from. Then L2TP creates a tunnel between the connection endpoints, and data is packed twice: originally by L2TP, then by the IPSec protocol.<\/p>\n\n\n\n

To enhance security, most VPNs will offer L2TP bundled with IPSec.<\/p>\n\n\n\n

L2TP Passthrough<\/h3>\n\n\n\n

An L2TP connection needs to go through a router to access the web and transfer its traffic. Passthrough is a router feature you can use to activate or deactivate L2TP traffic on your router.<\/p>\n\n\n\n

Another instance where this technology is used is with Network Address Translation (NAT). This feature allows many internet-connected devices attached to a single network to use a single IP address and connection. The issue is that NAT doesn\u2019t work well with L2TP. However, enabling L2TP Passthrough on your router will solve this problem.<\/p>\n\n\n\n

Benefits and Drawbacks of L2TP<\/h2>\n\n\n\n

Before we move on to comparisons of L2TP with other VPN protocols, we\u2019ll sum up some of its main pros and cons.<\/p>\n\n\n\n

On the one hand:<\/p>\n\n\n\n