MS-CHAP Authentication Failing When Connecting Draytek L2TP/IPSec VPN on Ubuntu Linux AWS EC2 Instance

Connecting to an L2TP/IPSec VPN provided by a Draytek router on a headless Ubuntu Linux AWS EC2 instance can be a bit tricky, but it's definitely possible. Here's a step-by-step guide to help you achieve this.

Prerequisites

Before we begin, ensure that you have the following prerequisites:

1. An AWS EC2 instance running Ubuntu Linux.
2. A Draytek router with L2TP/IPSec VPN settings configured.
3. Access to the EC2 instance through SSH.

Install Network Manager

The Network Manager is a powerful tool for managing network connections in Linux. Install it using the following command:

sudo apt-get update
sudo apt-get install network-manager network-manager-l2tp

Configure L2TP/IPSec VPN Connection

1. Open the Network Connections window:

   nm-connection-editor
   

2. Click on the 'Add' button to create a new connection.

3. Select 'VPN' as the connection type, and then 'L2TP' as the VPN type.

4. Fill in the connection details as follows:

   • Connection Name: Enter a name for your VPN connection.
   • Gateway: Enter the IP address of your Draytek router.
   • DNS servers: Enter the DNS server addresses provided by your VPN provider.
   • User Name: Enter your VPN username.
   • Password: Enter your VPN password.
   • L2TP Settings: Tick the 'Use L2TP/IPSec with pre-shared key' box.
   • IPSec Settings: Enter the IPSec pre-shared key provided by your VPN provider.

5. Click on the 'IPsec AuthenticationMethod' dropdown and select 'SHA1 with MD5' for compatibility with older Draytek routers.

6. Click on the 'SecurityMethod' dropdown and select '3DES' for compatibility with older Draytek routers.

7. Click on the 'AdvancedOptions' button, tick the 'Send PPP Echo Packets' box, and set the 'Idle time before terminating inactive connection (s)' to 0.

8. Click on the 'OK** button to save your settings.

Connect to the VPN

1. Click on the Network icon in your system tray, and select your VPN connection from the list.

2. Enter your VPN password when prompted.

3. Your system should now connect to the VPN.

Troubleshooting

If you encounter issues while connecting to the VPN, try the following troubleshooting steps:

1. Check your VPN settings on the Draytek router to ensure they are correct.
2. Make sure that the IPSec pre-shared key is entered correctly.
3. Try using different IPSec authentication and security methods.
4. Ensure that the 'Send PPP Echo Packets' option is enabled.
5. Check the logs for any error messages.

References

1. Ubuntu Manual: Setting up L2TP/IPSec VPN
2. Draytek L2TP/IPSec VPN Configuration Guide