While Paessler always encourages using the (which in mid‑2026 is beyond version 25.x), older releases such as 21.0.x are generally no longer available for direct download from the official website. However, users who have a valid maintenance agreement can access the complete archive of previous versions through their Paessler shop account.
Version 21.0.x optimized native cloud sensors for Microsoft Azure, Amazon Web Services (AWS), and Google Cloud Platform (GCP). These sensors track resource utilization, API thresholds, and billing budgets without requiring external plugins. System Requirements for PRTG 21.0.x
PRTG uses a proprietary database optimized for time-series data. Understanding its architecture is essential for a reliable 21.0.x deployment. Core Server vs. Remote Probes prtg network monitor 21.0.x
If you want to fine-tune your monitoring environment further, let me know:
A sensor in PRTG is a single monitoring metric. For example: One ping to an IP address. One CPU load metric on a server. One traffic counter on a switch port. One specific SQL database query. While Paessler always encourages using the (which in
Discovery and Inventory
Alerts in PRTG go beyond basic "Up/Down" states. You can configure: Core Server vs
PRTG 21.0.x continues to support standard protocols out of the box: For routers, switches, and firewalls. WMI / WinRM: For agentless Windows server management. SSH: For Linux and Unix systems.
PRTG 21.0.x offers three ways to interact with your data, all optimized during this release cycle: