Fixing Fortinet VPN Connection Problems Caused by Intune Certificate Deployment Failures

Troubleshooting Fortinet VPN Certificate Issues: A Step-by-Step Guide

Scenario: Your organization manages over 2000 devices, including desktops and laptops running Windows 7, 10, and 11. These devices are managed through Microsoft Intune and SCCM, with Microsoft Defender providing security. Security baseline policies are pushed across all devices, even those not directly managed by Intune or SCCM, through Microsoft Defender Intune integration.

Recently, an activity was planned to change the certificate on the Fortinet EMS server. The new certificate requires users to authenticate themselves while connecting to the VPN. Unfortunately, post-implementation, some devices failed to connect because they lacked the new certificate.

1. Step-by-Step Troubleshooting Approach

Let's first walk through the troubleshooting steps to identify and resolve the issue of missing or improperly installed certificates.

Step 1: Verify Certificate Deployment

• Check Intune Deployment Status:
• Review SCCM Deployment (if applicable):

Step 2: Check Device Certificate Store

• Access Certificates MMC:On the affected device, open certmgr.msc and navigate to the Personal > Certificates store.Verify if the new certificate is present. If missing, this confirms the certificate was not properly deployed.

Step 3: Review Intune/SCCM Policy Settings

• Check Intune Certificate Profile Configuration:Ensure the certificate profile is correctly configured and assigned to the proper device or user groups.If using SCCM, confirm the deployment settings and collections are correctly configured for all affected devices.

Step 4: Manually Install the Certificate (if needed)

• Export the Certificate from a Working Device:If some devices are missing the certificate, manually export the certificate from a device where the deployment was successful.Import it onto the affected devices using the Certificates MMC or command-line tools like certutil.

Step 5: Verify VPN Client Configuration

• Check VPN Client Settings:Open the Fortinet VPN client on affected devices.Verify that the correct certificate is selected under the Settings > Certificate section of the VPN client.

Step 6: Network Connectivity Verification

• Check Device Network Connectivity:Ensure the affected devices have active internet connections and can communicate with Intune.If using corporate VPNs, ensure that firewall rules and proxies are not blocking Intune’s communication or the certificate push.

Step 7: Review Logs and Event Viewer

• Gather Logs:Collect logs from the Fortinet VPN client and Windows Event Viewer to look for any errors related to certificate authentication or VPN connection failures.The Event Viewer can reveal if the certificate failed to load or if there are network issues preventing the VPN from connecting.

2. Certificate Distribution Process Using Intune

Now, let's dive into the Certificate Distribution Process to better understand the backend steps that are critical to deploying the new certificate and what might have gone wrong during deployment.

Prerequisites:

• Device Enrollment in Intune: Devices must be enrolled and actively managed through Intune.
• Certificate Authorities (CAs): Ensure the trusted Root Certification Authorities (CA) are set up for the certificate profile.
• Network Connectivity: Devices must have proper internet access and open ports for Intune communication.
• Certificate Profile Setup: A valid certificate profile must be created and deployed via Intune to manage the certificate push.

Certificate Deployment Workflow:

1. Create a Certificate Profile:
2. Assign the Profile:
3. Deploy the Profile:

Required Ports for Intune Communication:

• Port 443 (HTTPS): Secure communication between Intune and managed devices.
• Port 80 (HTTP): Fallback for connections if HTTPS fails.
• Port 2195/2196: APNs for Apple device management.
• Port 5671/5228: Push notification for updates.

3. Impact of Internet Disconnection During Certificate Deployment

Understanding how internet connectivity impacts certificate distribution is key when troubleshooting issues with devices that fail to receive the new certificate.

What Happens if the Internet Disconnects During Deployment?

• Certificate Object Creation:
• How to Identify if the Certificate Was Installed:
• Effect on VPN Functionality:

4. Preventive Measures for Future Activities

To avoid similar issues in the future, consider the following preventive measures:

Pre-Deployment Testing

• Before deploying the certificate change organization-wide, conduct a pilot test with a small group of devices to ensure the deployment process works smoothly.

Effective Communication

• Inform users about the certificate change and the potential impact on their VPN connections.
• Provide clear instructions on how to re-authenticate or troubleshoot if they encounter issues.

Implement Fallback Mechanisms

• Always retain the old certificate for a short period after deployment to provide a fallback if issues arise.
• This ensures that users with connectivity problems still have a chance to authenticate and connect until their devices receive the new certificate.

Automated Monitoring and Alerts

• Set up monitoring within Intune or SCCM to automatically track the success and failure of certificate deployments.
• Use alerts to notify administrators when a deployment fails or when a device has not received the certificate.

Routine Device Updates and Patching

• Regularly update all devices to avoid compatibility issues, especially with new security certificates.
• Ensure that devices are up to date with the latest Windows patches, especially before deploying security certificates.

Clear Documentation and Support Training

• Maintain comprehensive documentation on the certificate deployment process and troubleshooting steps.
• Provide training to support teams so they can efficiently handle issues related to VPN certificates and other network connectivity challenges.

Conclusion

By following the structured troubleshooting steps outlined above, you can quickly identify the root cause of VPN connectivity issues related to certificate distribution and resolve them efficiently. Understanding the certificate deployment process, ensuring stable internet connectivity during deployment, and implementing preventive measures will help avoid disruptions in the future. With proper planning, monitoring, and communication, your team can ensure a seamless certificate update process for Fortinet VPN clients and prevent connectivity issues for users.