General introduction to WMI and PRTG

Every so often customers using our monitoring tools (e.g. PRTG Network Monitor) report issues when trying to monitor their systems using WMI (Windows Management Instrumentation) sensors. In most cases, these issues stem from a malfunctioning WMI configuration/installation. For example, we have noticed that many times when WMI issues arise one (or multiple) WMI components crucial for proper WMI monitoring are missing or have not been implemented properly.

Getting started

Important! Before going any deeper into troubleshooting, a good knowledge of the principles and functions of WMI is necessary. Please refer to the following Microsoft article for frequently asked questions about WMI:

• Secrets of Windows Management Instrumentation

Basic requirements

Please ensure the following:

• The user whose credentials are specified for monitoring WMI is a member of the Domain Administrators group in the same Active Directory as the target computer. In case of a target computer outside a domain the user has to be a member of the local Administrators group and of the DCOM group on this machine.
• The monitoring user’s access rights on COM and WMI include remote access rights for the target computer. Read about Securing a Remote WMI Connection on MSDN.
• The target computer's Windows Firewall is set to allow WMI. MSDN features an article on this topic for XP and W2k3: Connecting Through Windows Firewall. For computers with Vista and above read this article on MSDN: Connecting to WMI Remotely Starting with Windows Vista.
• If the firewall is enabled by group policies you have to enable the "Allow Remote Administration Exception" as outlined in this article at Addicted to IT: Group Policy: Windows Firewall setting to allow your WMI scripts to run
• The RPC server used for WMI on the target computer is running on the port specified in PRTG (135 by default).
• Security Software: It's always a good idea to double-check that no local security software (anti-spy, anti-virus, etc.) on either side is blocking WMI connections.

Troubleshooting in detail

Please refer to the following articles for further information:

• WMI Tools Overview
• The most common WMI errors
• PRTG WMI error messages (PE code)

A very good external article for troubleshooting WMI is found here:

• WMI Troubleshooting Tips on technet.com

PRTG settings for WMI

PRTG offers a few settings for dealing with WMI issues:

• WMI Compatibility Options

Tips and Tricks

The following articles provide guidelines for special scenarios:

• How can I monitor WMI sensors if the target machine is not part of a domain?

How to repair WMI

If all else fails we've gathered some procedures which might fix the WMI system on affected computers:

• The Repair List for WMI problems

Further Reading

Another good article about all things regarding WMI can be found under:

http://msdn.microsoft.com/en-us/library/aa394572.aspx

This reference provides a list of WMI providers, information on the COM API for WMI, WMI queries, WMI log files, WMI security, WMI tools and WMI infrastructure objects and values.

Further articles of interest (providing more detail than the troubleshooting articles above), relating to particular aspects of WMI configuration can be found under :

• Connecting to WMI on a Remote Computer
• Creating a Connection to a WMI Namespace
• Very concise list of error codes (and their causes)
• Information relating to WMI character classes