Integrating Duo Two-Factor Authentication with Meraki Client VPN offers a robust solution to secure VPN logins through a streamlined, dual-layer security process. In today’s threat landscape, where safeguarding corporate resources is more critical than ever, the combination of Meraki’s SSL-encrypted Client VPN and Duo’s dynamic two-factor authentication provides an extra assurance layer that the right users gain access while keeping malicious attempts at bay.
Key takeaways include:
• Leveraging existing primary authentication (using Active Directory/LDAP or RADIUS) as the foundation.
• Installing a dedicated Duo Authentication Proxy to mediate between the Meraki MX and your authentication servers.
• Carefully configuring parameters in the authproxy.cfg file to tie the Vault of secrets (API keys and shared secrets) into the overall security framework.
A few practical recommendations:
• Study Duo Administrator documentation for guidance on application protection and user access configurations.
• Confirm that your test users have been granted explicit access within Duo’s settings, ensuring that when you test the VPN login, the second factor prompt appears as expected.
• Note that the secret key provided by Duo must be treated with the same care as any sensitive password. Maintaining its integrity is essential to preserving the security of your deployment.
• Windows Server 2016 or later
• CentOS Stream 9, Fedora 39, or Red Hat Enterprise Linux 7 (and later)
• Ubuntu 20.04 LTS, Debian 11, or other modern Linux distributions
• Rocky Linux 9 or later
For Windows users, it is strongly advised not to install the Duo proxy on the same server servicing your Active Directory domain controller or running the Network Policy Server (NPS) role. If co-location is unavoidable, be prepared to resolve conflicts—particularly over LDAP or RADIUS ports—that might otherwise impede performance.
C:\Program Files\Duo Security Authentication Proxy\conf\authproxy.cfg
For Linux, the configuration usually resides in /opt/duoauthproxy/conf/authproxy.cfg.
The [radius_server_auto] section must include:
• Your Duo integration key (ikey), secret key (skey), and API hostname—these are provided by Duo once you set up the Meraki RADIUS VPN application in the Duo Admin Panel.
• The IP address of your Meraki MX, ensuring that only approved clients with matching shared secrets can send RADIUS requests to the proxy.
• A RADIUS secret shared between your proxy and the Meraki MX.
• The identification of which primary authenticator should be used—whether it’s using the active directory settings ([ad_client]), the RADIUS settings ([radius_client]), or even a duo_only client if you opt out of primary authentication.
The detailed configuration helps ensure that the proxy correctly intercepts authentication requests, validates them with the primary authenticator, and then leverages Duo’s secure push notifications or other two-factor methods to complete the authentication process.
• Editing the authproxy.cfg file with real-time syntax suggestions
• Validating configuration changes before saving
• Starting or stopping the proxy service
• Monitoring proxy status and logs
Using this utility simplifies the management of deployment—especially when troubleshooting configuration errors or updating parameters for evolving security requirements. However, note that the Proxy Manager is only available on Windows; Linux administrators must rely on text editors and command-line tools to tweak their configuration files.
• Always back up your existing configuration files before making changes. This way, if a new configuration causes unexpected issues, you can quickly revert to the previous state.
• Test the configuration with a small set of users first before rolling it out organization-wide. This phased approach minimizes disruptions and allows for any necessary tweaks based on real-world performance.
• Keep your operating environment updated. For instance, if your Meraki Client VPN software is outdated, contact support to adjust settings like the RADIUS timeout.
• Maintain strict control over sensitive credentials. Your Duo secret key and shared secrets should be treated with the highest level of security—avoid sharing them via email or any unsecured communication channels.
• Document changes thoroughly. Whether you update the Duo proxy installation, modify primary authenticator settings, or adjust the Meraki integration, keeping clear records aids in troubleshooting and future audits.
• Monitor logs and alerts regularly. Duo provides valuable feedback through its logs that can alert you to both successful and failed authentication attempts, which is critical for proactive security management.
For Windows administrators, this integration aligns perfectly with broader security trends. Modern Windows networks are under constant threat, and combining Windows-based services with enhanced, multi-factor authentication creates an environment that is inherently more resilient against breaches. Moreover, the technical depth and flexibility of Duo’s solution echo the enterprise-grade security that many organizations demand today.
By carefully planning your deployment, ensuring that all components—whether Active Directory/LDAP or RADIUS—are correctly configured, and employing best practices in credential management and testing, you can achieve a secure, reliable VPN environment. As cybersecurity threats evolve, solutions like these illustrate the proactive measures that enterprises must adopt to protect their digital borders, and Windows environments, in particular, benefit from such industry-leading security integrations.
For IT professionals and network administrators, this integration not only enhances security but also serves as a practical case study in combining multiple authentication sources into a unified, resilient access control system—all while remaining aligned with the demands of modern enterprise IT.
Source: Duo Security Duo Two-Factor Authentication for Meraki Client VPN
A Quick Overview
Meraki’s Client VPN, when paired with Duo, supports push notifications, phone calls, and passcode methods for secondary authentication. This integration does not include the interactive Duo Prompt seen in web applications; rather, it enhances Windows and mobile client logins through simple RADIUS-based configurations. For organizations running software versions prior to MX 16.14, an update in the Client VPN RADIUS Timeout value (increased to 60 seconds) may be necessary—which means contacting Meraki Support before proceeding.Key takeaways include:
• Leveraging existing primary authentication (using Active Directory/LDAP or RADIUS) as the foundation.
• Installing a dedicated Duo Authentication Proxy to mediate between the Meraki MX and your authentication servers.
• Carefully configuring parameters in the authproxy.cfg file to tie the Vault of secrets (API keys and shared secrets) into the overall security framework.
Laying the Groundwork
Before embarking on the technical setup, administrators should familiarize themselves with fundamental Duo administration concepts. It’s worthwhile to review available enrollment methods, Duo policy settings, and application options within the Duo Admin Panel. Most importantly, ensure your primary authentication configuration is fully operational for your Meraki MX users. This will save time troubleshooting later if the primary authentication fails or misconfigurations arise.A few practical recommendations:
• Study Duo Administrator documentation for guidance on application protection and user access configurations.
• Confirm that your test users have been granted explicit access within Duo’s settings, ensuring that when you test the VPN login, the second factor prompt appears as expected.
• Note that the secret key provided by Duo must be treated with the same care as any sensitive password. Maintaining its integrity is essential to preserving the security of your deployment.
Setting Up the Duo Authentication Proxy
At the heart of the integration lies the Duo Authentication Proxy—a mediator that intercepts RADIUS requests from your Meraki MX and performs the dual role of primary user authentication (via LDAP/Active Directory or RADIUS) and subsequent secondary authentication via Duo’s cloud services.Choosing the Right Host and Operating System
For optimal performance, the proxy should be installed on a dedicated machine. Recommended operating systems include:• Windows Server 2016 or later
• CentOS Stream 9, Fedora 39, or Red Hat Enterprise Linux 7 (and later)
• Ubuntu 20.04 LTS, Debian 11, or other modern Linux distributions
• Rocky Linux 9 or later
For Windows users, it is strongly advised not to install the Duo proxy on the same server servicing your Active Directory domain controller or running the Network Policy Server (NPS) role. If co-location is unavoidable, be prepared to resolve conflicts—particularly over LDAP or RADIUS ports—that might otherwise impede performance.
Installation Instructions for Windows and Linux
Duo offers tailored installation packages for both Windows and Linux environments:- Windows Installation:
• Download the latest Duo Authentication Proxy installer (the filename typically reflects the version, e.g., duoauthproxy-6.4.2.exe).
• Run the installer with elevated rights. You have the option to install the Proxy Manager, a handy Windows utility that not only helps edit the authproxy.cfg file but also provides a visual status of your proxy service. For a silent installation, use the command line with switches such as /S for a silent setup.
• If you opt-out of installing the Proxy Manager, simply deselect it during the component selection step. - Linux Installation:
• Download the source package using tools like wget or curl. The file is typically referred to as duoauthproxy-6.4.2-src.tgz (the version number will vary).
• Extract the package, navigate to the directory, and compile using standard tools (gcc, make, libffi-devel, zlib-devel, and diffutils are common dependencies).
• Follow the on-screen prompts during the installation script to configure the proxy’s runtime user, log group, and, if necessary, the SELinux module.
Configuration Essentials
Once the Duo Authentication Proxy is installed, its operation pivots on the authproxy.cfg configuration file, located by default in different directories depending on your OS. For Windows (version 5.0.0 and later), the path is typically:C:\Program Files\Duo Security Authentication Proxy\conf\authproxy.cfg
For Linux, the configuration usually resides in /opt/duoauthproxy/conf/authproxy.cfg.
Configuring Your Primary Authenticator
At this stage, you decide whether your primary authentication will rely on Active Directory/LDAP or a RADIUS server.- Active Directory/LDAP Integration ([ad_client] Section):
Here, you specify crucial details such as:
• The hostname or IP address of your directory server.
• A service account’s username and password, which has permission to perform directory searches (ideally configured with read-only rights).
• The distinguished name (DN) for searching the relevant user container.
• Optionally, a security group DN to restrict access only to authorized users.
This setup is particularly compelling for Windows-centric environments where Active Directory is the backbone of identity management. An example configuration might look like:
[ad_client]
host=1.2.3.4
host_2=1.2.3.5
service_account_username=duoservice
service_account_password=your_password_here
search_dn=DC=example,DC=com
security_group_dn=CN=DuoVPNUsers,OU=Groups,DC=example,DC=com - RADIUS Integration ([radius_client] Section):
If you prefer using an existing RADIUS server for primary authentication, you can configure the proxy accordingly by setting parameters like:
• The IP address of the RADIUS server.
• A shared secret that both the RADIUS server and the proxy know.
• Optional fallback servers in case your primary RADIUS server is unreachable.
• By default, the authentication port used is 1812, unless you specify otherwise to avoid conflicts.
Tying It All Together with Meraki MX
After configuring your primary authentication source, it's time to integrate Meraki MX settings. In the Duo Authentication Proxy configuration file, create a [radius_server_auto] section. This section completes the integration by connecting the Duo proxy to your Meraki MX and Duo services.The [radius_server_auto] section must include:
• Your Duo integration key (ikey), secret key (skey), and API hostname—these are provided by Duo once you set up the Meraki RADIUS VPN application in the Duo Admin Panel.
• The IP address of your Meraki MX, ensuring that only approved clients with matching shared secrets can send RADIUS requests to the proxy.
• A RADIUS secret shared between your proxy and the Meraki MX.
• The identification of which primary authenticator should be used—whether it’s using the active directory settings ([ad_client]), the RADIUS settings ([radius_client]), or even a duo_only client if you opt out of primary authentication.
The detailed configuration helps ensure that the proxy correctly intercepts authentication requests, validates them with the primary authenticator, and then leverages Duo’s secure push notifications or other two-factor methods to complete the authentication process.
Managing the Duo Authentication Proxy
For those running the proxy on Windows, the Duo Authentication Proxy Manager is an invaluable tool. Accessible through the Start Menu under Duo Security, it provides a graphical interface for:• Editing the authproxy.cfg file with real-time syntax suggestions
• Validating configuration changes before saving
• Starting or stopping the proxy service
• Monitoring proxy status and logs
Using this utility simplifies the management of deployment—especially when troubleshooting configuration errors or updating parameters for evolving security requirements. However, note that the Proxy Manager is only available on Windows; Linux administrators must rely on text editors and command-line tools to tweak their configuration files.
Practical Considerations and Best Practices
When undertaking a Duo-Meraki VPN integration, consider the following best practices to ensure a smooth deployment:• Always back up your existing configuration files before making changes. This way, if a new configuration causes unexpected issues, you can quickly revert to the previous state.
• Test the configuration with a small set of users first before rolling it out organization-wide. This phased approach minimizes disruptions and allows for any necessary tweaks based on real-world performance.
• Keep your operating environment updated. For instance, if your Meraki Client VPN software is outdated, contact support to adjust settings like the RADIUS timeout.
• Maintain strict control over sensitive credentials. Your Duo secret key and shared secrets should be treated with the highest level of security—avoid sharing them via email or any unsecured communication channels.
• Document changes thoroughly. Whether you update the Duo proxy installation, modify primary authenticator settings, or adjust the Meraki integration, keeping clear records aids in troubleshooting and future audits.
• Monitor logs and alerts regularly. Duo provides valuable feedback through its logs that can alert you to both successful and failed authentication attempts, which is critical for proactive security management.
The Broader Security Implications
Integrating Duo’s two-factor authentication pushes the envelope in securing remote access, particularly important in environments increasingly reliant on VPNs. The addition of a secondary authentication factor mitigates the risk posed by stolen or weak primary credentials—a vulnerability exploited all too often in today’s cyberattacks.For Windows administrators, this integration aligns perfectly with broader security trends. Modern Windows networks are under constant threat, and combining Windows-based services with enhanced, multi-factor authentication creates an environment that is inherently more resilient against breaches. Moreover, the technical depth and flexibility of Duo’s solution echo the enterprise-grade security that many organizations demand today.
Final Thoughts
The Duo Two-Factor Authentication for Meraki Client VPN is a prime example of how layered security strategies can be effectively implemented. It takes the best of Meraki’s VPN capabilities and bolsters them with Duo’s robust secondary authentication process—safeguarding access and ensuring that only verified users gain entry into critical network resources.By carefully planning your deployment, ensuring that all components—whether Active Directory/LDAP or RADIUS—are correctly configured, and employing best practices in credential management and testing, you can achieve a secure, reliable VPN environment. As cybersecurity threats evolve, solutions like these illustrate the proactive measures that enterprises must adopt to protect their digital borders, and Windows environments, in particular, benefit from such industry-leading security integrations.
For IT professionals and network administrators, this integration not only enhances security but also serves as a practical case study in combining multiple authentication sources into a unified, resilient access control system—all while remaining aligned with the demands of modern enterprise IT.
Source: Duo Security Duo Two-Factor Authentication for Meraki Client VPN
