Choosing a VPN protocol can feel like trying to learn a new language. You likely see acronyms like L2TP, OpenVPN, and WireGuard in your app settings and wonder which one actually keeps your data safe.
In this guide, we will break down what L2TP is, how it protects (or doesn’t protect) your information, and why it is almost always paired with another technology called IPsec.
Key takeaways:
- L2TP is a tunneling protocol that must pair with IPsec to provide actual data encryption.
- L2TP remains popular for corporate use to bridge remote employees with office networks safely.
- L2TP is built into Windows and macOS, so you don’t need to install additional software.
- L2TP is often blocked by firewalls and runs slower than modern protocols because it wraps data twice.
- L2TP is considered legacy in 2025, with WireGuard or IKEv2 being the preferred choices for speed.
1. What is L2TP VPN? A simple definition
L2TP stands for Layer 2 Tunneling Protocol. Think of it as a digital construction crew that builds a private tunnel through the public internet. This tunnel allows data to travel between your device and a VPN server without being seen by others on the same network.
The history of this protocol is a story of collaboration. In the late 1990s, the Internet Engineering Task Force (IETF) wanted to create a single, better standard for tunneling. They combined two older systems (L2F from Cisco and PPTP from Microsoft) to create L2TP.
The result was formalized in RFC 2661. However, there is a catch. While L2TP is excellent at building tunnels, it does not have any “locks.” On its own, it does not encrypt your data. If you used L2TP by itself, a hacker could still “look inside” the tunnel and read your passwords or emails.
2. What is L2TP/IPsec?
Because L2TP lacks security, it is rarely used alone. Instead, it works in a “buddy system” with IPsec (Internet Protocol Security). When you see L2TP in a menu, it is almost certainly L2TP/IPsec.
In this partnership, each protocol has a specific job:
- L2TP builds the tunnel and manages the connection.
- IPsec handles the encryption, data integrity, and authentication.
This combination is defined by RFC 3193. It ensures that your data is not only hidden inside a tunnel but also scrambled into a code that only the intended receiver can read. If an intruder manages to intercept a data packet, they would only see a jumble of meaningless characters.
3. How does L2TP VPN work?
To understand how L2TP works, imagine you are sending a letter. Most protocols put your letter in an envelope. L2TP, however, uses a process called double encapsulation to build a secure path through a public network.
3.1. Double encapsulation (2-layer data wrapping)
L2TP, when paired with IPsec, uses a two-step process to wrap your data.
First, it wraps your data in a PPP session (Point-to-Point Protocol) to establish the initial connection. During this stage, L2TP assigns IP addresses provided by your Internet Service Provider (ISP) to both ends of the tunnel. This step is critical because it allows control packets to travel through the tunnel correctly.
Once the tunnel is ready, it wraps that entire package again inside an IPsec layer for encryption. This layer uses sophisticated methods like 256-bit AES to ensure confidentiality and integrity.
While this two-step process keeps your data safe even on public networks, the extra “wrapping” is also why your internet speed might drop slightly compared to other methods.
3.2. LAC and LNS (tunnel endpoints)
The tunnel has two main “gates” or components that manage the flow of data:
- L2TP Access Concentrator (LAC): This functions at the originating point of the tunnel. It sits on your device or local network, accepts the client connection, and initiates the tunnel with the server.
- L2TP Network Server (LNS): This is the endpoint located at the VPN provider’s office or your company’s headquarters. It acts as a bridge, connecting the secure tunnel to the target network or private resources you are trying to reach.
3.3. Ports, IKE, and NAT Traversal
For the connection to be successful, it must pass through specific “gates” or ports registered with the Internet Assigned Numbers Authority (IANA). It also uses specific protocols to verify that both sides are who they say they are:
- Internet Key Exchange (IKE): This protocol works alongside IPsec to establish mutual authentication between your device and the server, ensuring a secure “handshake” before data moves.
- UDP Port 1701: Reserved for the L2TP tunnel itself.
- UDP Port 500: Used for the IKE process and exchanging security keys.
- UDP Port 4500: Used for NAT Traversal, which helps the VPN function properly even if your router is using a private IP address.
4. What is L2TP Passthrough?
L2TP Passthrough is a router setting that allows your VPN traffic to bypass your firewall. It acts like a green light, letting encrypted data flow freely between your device and the VPN server without being blocked.
Most home routers use a system called NAT (Network Address Translation). This system can sometimes get confused by the complex way L2TP/IPsec wraps its data, leading to a failed connection. Enabling passthrough creates a dedicated lane for this specific traffic to move through.
You can typically find this option in your router’s settings under one of these labels:
- L2TP Passthrough: The most direct label for this feature.
- IPsec Passthrough: Sometimes required because L2TP depends on IPsec for security.
- VPN Passthrough: A general category that often includes L2TP support.
5. Is L2TP VPN secure enough for modern standards?
When L2TP/IPsec uses modern encryption like AES-256 (Advanced Encryption Standard), it is considered very secure for most daily tasks. AES-256 is widely approved for government and enterprise use when properly implemented.
The National Institute of Standards and Technology (NIST) Special Publication 800-77 provides guidelines on IPsec VPNs, recognizing IPsec as a robust method to protect data when properly implemented. However, as we move through 2025, security experts have noted a few potential concerns:
- The NSA Question: There have been unverified claims that some older versions of the protocol might have “backdoors” or weaknesses that intelligence agencies could exploit.
- Pre-Shared Keys (PSK): Many L2TP setups use a simple password (the PSK) for the first step of the connection. If this password is weak or shared publicly, the security of the entire tunnel is at risk.
6. Pros and cons of using L2TP/IPsec
Every protocol has trade-offs between speed, ease of use, and security. L2TP is often seen as a reliable “middle ground” option for many users.
The advantages include:
- High compatibility: It is a native protocol on Windows, macOS, and iOS.
- Easy setup: You do not usually need to download third-party apps to make it work.
- Stable connection: It is generally more reliable than the older PPTP protocol.
The disadvantages include:
- Slower speeds: The double encapsulation process requires more CPU power.
- Firewall issues: It is easily blocked by network administrators because it uses fixed ports.
- Potential leaks: If the IPsec connection drops, your data might be exposed for a few seconds.
7. L2TP vs other protocols
If you are wondering how L2TP stacks up against the competition, we have compared the most common protocols below.
7.1. L2TP/IPsec vs. PPTP
PPTP is the “grandfather” of VPN protocols. While it is very fast, it is now considered insecure and can be cracked in minutes. L2TP/IPsec is much safer than PPTP because it uses more modern encryption methods.
7.2. L2TP/IPsec vs. SSTP
SSTP (Secure Socket Tunneling Protocol) is primarily owned by Microsoft. It is excellent at bypassing firewalls because it uses Port 443 (the same as normal websites). However, it is not as widely available on non-Windows devices compared to L2TP.
7.3. L2TP/IPsec vs. IKEv2
IKEv2 is often considered the “next step” after L2TP. It is much faster and is specifically designed for mobile users. If your phone switches from Wi-Fi to 4G, IKEv2 stays connected, whereas L2TP often drops the connection.
7.4. L2TP/IPsec vs. OpenVPN
OpenVPN is the “gold standard” for flexibility. It can hide its traffic to look like regular web browsing, making it better for bypassing firewalls. However, it usually requires you to install a separate app, unlike L2TP which is built-in.
7.5. L2TP/IPsec vs. WireGuard
WireGuard is the modern favorite for 2025. It uses much newer code, which makes it significantly faster than L2TP and easier on your battery life. If your VPN provider offers WireGuard, it is generally the best choice for speed.
| Protocol | Key Advantages | Security | Compatibility |
|---|---|---|---|
| L2TP/IPsec | Built-in, no app required. | Secure (AES-256). | Windows, macOS, legacy devices. |
| PPTP | Fast but obsolete. | Very Low (Easily cracked) |
Phasing out; legacy only. |
| SSTP | Bypasses firewalls (Port 443). | High (Microsoft proprietary). | Windows-optimized. |
| IKEv2 | Stable network switching (Wi-Fi/4G). | High (Modern suites). | Mobile & modern laptops. |
| OpenVPN | Highly flexible & versatile. | High (Open-source/Audited). | Requires 3rd-party apps. |
| WireGuard | Fastest & battery-efficient. | High (Modern crypto). | 2025 industry standard. |
8. When should you still use an L2TP VPN?
Even though newer protocols exist, L2TP still has a place in the tech world.
You should use L2TP if:
- You are using legacy hardware, such as an older office router or a smartphone from five years ago that doesn’t support newer apps.
- Your company’s IT department requires it for remote access and has already configured the security keys for you.
- You want a quick connection and don’t want to install any third-party VPN software.
You should NOT use L2TP if:
- You are trying to stream high-definition 4K video and need the absolute fastest speeds.
- You are in a country with strict internet censorship, as the connection will likely be blocked.
- You are performing highly sensitive tasks where you want the most modern encryption available (like WireGuard).
9. FAQs about what is L2TP VPN
Is L2TP better than IKEv2?
Typically, no. IKEv2 is more modern, faster, and more stable for mobile users. While L2TP is highly compatible with older systems, IKEv2 is the superior choice for modern smartphones and laptops.
Does L2TP hide my IP address?
Yes. Once the tunnel is established, your real IP address is hidden. Websites and apps will see the IP address of the VPN server instead of your home or mobile connection.
Why is my L2TP VPN slow?
This is usually caused by the “double encapsulation” process. Your device has to encrypt and wrap every piece of data twice. On older devices, this extra work can slow down your internet speed.
Can I use L2TP without IPsec?
Technically, yes, but you should never do it. Without IPsec, your data has no encryption. This would be like sending a postcard with your bank details written on the back; anyone who sees it can read it.
10. Conclusion
Understanding what is L2TP VPN helps you make better decisions about your online privacy. While it is an aging protocol, its “double-wrapped” security and built-in compatibility make it a reliable fallback for many users, especially on older devices.
However, if speed and bypassing firewalls are your main priorities in 2025, you might find that newer options like WireGuard offer a better experience. L2TP remains a trusted “workhorse” of the internet, but it is no longer the only (or the fastest) option available.
To find more helpful guides, visit our Privacy & Security Basics category at Safelyo.
