The L2TP Connection Attempt Failed Because The Security Layer Encountered a Processing Error – [FIX]

About The L2TP Connection Attempt Failed Because The Security Layer Encountered a Processing Error:

An L2TP connection uses layer 2 Tunneling Protocol to encrypt and support Virtual Private Networks. A Virtual Private Network (VPN) is mainly used to hide the original connection by reflecting the connection over a server located in a different area than the connection’s origin. This helps people in hiding their locations from certain websites, thus bypassing some security restrictions.

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However, in some cases, users are unable to make a VPN connection, and “The L2TP connection attempt failed because the security layer encountered a processing error during the initial negotiations with the remote computer” Error is displayed while trying to do so. 

Causes for the “L2TP Connection Attempt Failed” Error

The causes due to which it is triggered are as follows:

  1. Disabled Protocols: It has been seen that the Error is triggered in most cases when the Microsoft CHAP v2 protocol is disabled inside the VPN Connection’s properties. So, for most VPN connections to perform, this protocol needs to be enabled.
  2. PPP Settings: Users need to properly configure the Point to Point protocol before attempting a VPN connection. This protocol has an LCP protocol with some further extensions that must be enabled so the connection works properly.

Steps to connect to L2TP

  1. On the Windows taskbar, click on the “Network” icon. There will appear a list of available VPNs and networks.
  2. Now click on the “VPN” connection. Network and Internet VPN settings get displayed then.connect to l2tp
  3. Select the “VPN connection. Then click on the “Connect” button.
  4. Now enter your user name and password.
  5. Then click “OK”.

Methods To Fix The L2TP Connection Attempt Failed Because The Security layer encountered a processing error

There are several methods listed below. Follow the steps to resolve your issue.

Method 1: Enabling MS-CHAP v2

  1. First, ensure that the VPN connection has been properly configured to match the credentials of the VPN server you are trying to connect to, and then add the connection.
  2. In the network adapter list, the connection will appear once been added.
  3. To open the “Run” prompt, press “Windows” + “R”.
  4. Now type in “ncpa.cpl”, then press enter to open the Network Adapter Settings.ncpa
  5. Now right click on the “VPN” Connection that has been added, then select “Properties”.right-click vpn and select properties
  6. Then click on the “Security” tab and check the “Allow these protocols option”.allow these protocols
  7. Under the “Allow these protocols option”, check the “Microsoft-CHAP Version 2” and then click on “OK”.
  8. Now try connecting the VPN to check if the issue persists or not.

Method 2: Enabling LCP Extensions

To enable the LCP Extensions, it is important to configure the PPP (Point to Point Protocol) Settings. 

PPP Settings are configured through the following steps:

  1. To open the “Run” prompt, press “Windows” + “R”.
  2. Now type in “ncpa.cpl”, then press enter to open the Network Adapter Settings.
  3. Now right click on the “VPN” Connection that has been added, then select “Properties”.
  4. Then, click on the “Options” tab and select “PPP Settings”.
  5. Now check the “Enable LCP Extensions” and click on the “OK” button.ppp settings (the l2tp connection attempt failed because the security layer encountered a processing error)
  6. Again, click on the “OK” button to save your settings.
  7. Now try connecting the VPN to check if the issue persists or not.

Method 3: By Restarting IPSec Service (Fix The L2TP Connection Attempt Failed Because The Security Layer Encountered a Processing Error)

  1. To open the “Run” prompt, press “Windows” + “R”.
  2. Now type in “services.msc” and then press enter.services-msc
  3. The Service Manager Window will appear. Now go to the right side of the service manager and select the “Name” column. Under the name column, look for IKE and AuthIP IPSec Keying Modules.
  4. When it is running, right-click on it and select “Restart”.click on restart (the l2tp connection attempt failed because the security layer encountered a processing error)
  5. Now double-click on it and go to the Startup type section under the General tab in the properties window.
  6. Now set the field to Automatic.click automatic
  7. Then press “Apply” and click on the “OK” button to save the changes and exit.
  8. For the IPSec Policy Agent Service, repeat steps 3 and 4.
  9. Then restart the VPN connection to ensure it started working properly.

Method 4: By reinstalling the Network Adapter

  1. To open the “Run” prompt, press “Windows” + “R”.
  2. Now type in “devmgmt.msc” and then press enter.devmgmt
  3. The device manager window opens then. In that, navigate to the network adapter and then expand the section.
  4. After locating the network adapter for VPN, right-click on it and then select “Uninstall device”click uninstall device
  5. Click on the uninstall button to confirm the action.
  6. After it gets uninstalled, restart your PC.

The device then gets reinstalled automatically and reset to its default settings.

You must also check for a proper certificate used for both the client and the server. Ensure that PSK (Pre Shared Key), if used, is the same and whether configured for both the client and the VPN server or not.

Conclusion

In this article, we got to know about the l2tp connection attempt failed because the security layer encountered a processing error and the methods to solve this error. I hope you found this article helpful and your problem is resolved.

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