Prerequisites:

1. PRTG Installation: Ensure PRTG Network Monitor is installed and operational in your environment.
2. Access to SSL/TLS Endpoints: You need access to the SSL/TLS endpoints (e.g., web servers, application servers) where SSL/TLS certificates with multi-domain support are deployed.
3. Administrator Access: Obtain administrative privileges to configure sensors and settings in PRTG.

Setting Up SSL/TLS Certificate Monitoring:

1. Add SSL/TLS Endpoint(s): In PRTG, navigate to "Devices" and add the SSL/TLS endpoint(s) you wish to monitor.
2. Install SSL/TLS Certificate Sensor: Click on the SSL/TLS endpoint device you added, then go to "Add Sensor" > "By Type" > Select "SSL Certificate Sensor."
3. Configure Sensor Parameters: Define the parameters for monitoring, including the hostname or IP address of the SSL/TLS endpoint, port number, and monitoring intervals.
4. Select Monitoring Metrics: Choose the monitoring metrics you want to track, such as certificate subject alternative names (SANs), multi-domain usage, expiration date, and certificate issuer.
5. Test Configuration: Verify that the sensors can successfully retrieve SSL/TLS certificate information and monitor multi-domain usage.

Monitoring Multi-Domain Usage:

1. Real-time Monitoring: Access the PRTG dashboard to view real-time updates on SSL/TLS certificate multi-domain usage.
2. Subject Alternative Names (SANs): Monitor SSL/TLS certificate SANs to identify domains and subdomains covered by the certificate's multi-domain support.
3. Domain Coverage: Track the coverage of SSL/TLS certificates across multiple domains within the organization's network infrastructure, ensuring that all relevant domains are included and properly secured.
4. Certificate Rotation: Monitor SSL/TLS certificate rotation and renewal processes to ensure timely updates to multi-domain certificates and prevent service disruptions or security vulnerabilities.
5. Threshold-based Alerts: Set up threshold-based alerts to notify administrators when SSL/TLS certificate multi-domain coverage changes, when certificates approach expiration, or when anomalies are detected, indicating potential misconfigurations or security risks.

Best Practices:

1. Comprehensive Domain Coverage: Ensure comprehensive coverage of all relevant domains and subdomains within the organization's network infrastructure when deploying SSL/TLS certificates with multi-domain support, including primary domains, subdomains, and alternate domains.
2. Certificate Lifecycle Management: Implement robust certificate lifecycle management practices, including regular certificate rotation, renewal, and revocation procedures, to maintain SSL/TLS certificate validity and security.
3. Certificate Authority (CA) Validation: Verify that SSL/TLS certificates are issued by reputable and trusted certificate authorities (CAs) and that multi-domain certificates comply with CA/Browser Forum guidelines for certificate issuance and validation.
4. Domain Ownership Verification: Validate domain ownership and control for all domains and subdomains included in SSL/TLS certificate SANs to prevent unauthorized domain usage and ensure compliance with industry standards and best practices.
5. Centralized Certificate Management: Centralize SSL/TLS certificate management and monitoring processes using dedicated certificate management platforms or tools to streamline certificate provisioning, monitoring, and renewal workflows and improve operational efficiency.

Troubleshooting:

1. Connection Issues: Ensure that PRTG can establish HTTPS connections to the SSL/TLS endpoints and retrieve certificate information successfully.
2. Sensor Configuration: Double-check sensor settings, including hostname or IP address, port number, and monitoring intervals, and verify that the correct sensor type is used for monitoring SSL/TLS certificates.
3. Certificate Inspection: Review SSL/TLS certificate details, including SANs, expiration dates, and issuer information, to troubleshoot issues related to multi-domain usage or certificate misconfigurations.
4. Certificate Revocation Checking: Verify that SSL/TLS certificates are properly revoked if they are no longer needed or if they are compromised to prevent unauthorized multi-domain usage and maintain the trustworthiness of SSL/TLS communications.
5. Domain Validation: Validate domain ownership and control for all domains and subdomains covered by SSL/TLS certificate SANs to ensure that multi-domain certificates are issued only for authorized domains and prevent potential abuse or misuse of certificate multi-domain features.

By leveraging PRTG Network Monitor to monitor SSL/TLS certificate multi-domain usage, you can enhance the security and integrity of encrypted communications across multiple domains within the organization's network infrastructure. Real-time monitoring, proactive alerting, and comprehensive analysis enable you to detect and address multi-domain certificate issues promptly, strengthen cryptographic defenses, and safeguard sensitive data transmitted over the network. With PRTG, you can effectively manage and monitor SSL/TLS certificate multi-domain usage to meet the operational requirements and security goals of your organization.