You've set up PRTG and added devices to your monitoring environment. But are you sure you're monitoring everything that matters? Missing even one critical device can result in unexpected downtime, service interruptions, and those dreaded after-hours emergency calls. Let's ensure your monitoring is as comprehensive as your network.
When you first set up PRTG, it performs an auto-discovery in order to locate devices on your network. However, this process may overlook important devices for one simple reason: ICMP (Ping) may be disabled.
For auto-discovery to work properly, PRTG must be able to ping each target device. If a device doesn't respond to ICMP requests, PRTG won't find it during auto-discovery, leaving a potentially critical system unmonitored.
Let's solve this problem with two practical approaches:
The simplest solution is to enable ICMP responses on your devices. This allows PRTG to detect the devices during auto-discovery.
If security policies prevent you from enabling ICMP across your entire network, consider configuring an access control list (ACL) that only allows your PRTG server's IP address to ping these devices. This maintains security while enabling proper monitoring.
Once you've enabled ICMP, you have two options:
1️⃣ Manually add the previously missing devices to PRTG.
2️⃣ Run the auto-discovery process again to let PRTG find them automatically.
Networks are constantly changing. New devices are added, old ones are removed, and configurations are updated. To keep your monitoring up to date, set up scheduled auto-discoveries.
You can configure PRTG to automatically run an auto-discovery on a regular schedule—for example, every weekend. When an auto-discovery runs, it detects any new devices added to your network and creates appropriate sensors for them.
PRTG will create a ticket and notify you by email about the results of each auto-discovery run, whether or not new devices are found. For optimal performance, schedule these auto-discoveries during off-hours when there is minimal user activity on your network.
Watch this tutorial to see how to use auto-discovery effectively in PRTG:
Consider the following scenario: A company had three IP cameras in its security system, but PRTG only discovered two of them, Cam01 and Cam03. Despite being connected to the network and functioning normally, the third camera (Cam02) wasn't appearing in PRTG.
What was the issue? ICMP was disabled on Cam02 as part of the default configuration. After enabling ICMP responses on Cam02, the company was able to discover it via auto-discovery and proceed with monitoring.
✅ Review your list of critical systems and compare it with what's currently being monitored in PRTG.
✅ Check your firewall and device settings to ensure that ICMP is enabled for your PRTG server.
✅ Run a manual auto-discovery after making any changes to see if previously missing devices appear.
✅ Set up a scheduled auto-discovery to run weekly during off-hours.
✅ Document any devices that required manual addition for future reference.
Following these steps will give you confidence that your monitoring is truly comprehensive and that no critical devices are flying under your radar. Your monitoring will be more reliable, and you'll avoid the unpleasant surprise of discovering an unmonitored device only after it fails.
Want to dive deeper into auto-discovery capabilities? Check out the following links:
👉 How to run an auto-discovery in PRTG in 5 steps
Next week, we'll explore how to enhance your monitoring with vendor-specific sensors for deeper device insights. This will transform your monitoring from simple up/down status checks to detailed performance analytics that help you prevent problems before they affect your users.