Configuration Manager uses Wake-On-LAN (WOL) to awaken a powered-off device, perform requested actions (install or remove applications, install updates, etc.) and then power the computer OFF again, if desired. It’s a compromise between energy efficiency and management efficiency, and if configured correctly, does a great job in most cases. In Part 6 of my SCCM 2007 Client troubleshooting series I cover WOL problems.

David Stein

David is an author and consultant, working for Endurance IT Services in Virginia Beach, Virginia, specializing in Microsoft enterprise systems and Business Process Automation.

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Contents of this article

Symptoms
Potential causes
Suggestions
Helpful links

If you’re not really clear on what Wake-On LAN (WOL) is, and how it works, you should start by reading up on that first. Essentially (and this is not intended as a substitute for doing your homework), WOL is a mix of technologies, protocols and network communication that allows a computer to be powered OFF, but not completely. One small part of it remains awake, and listens to the network port for a special incoming request packet that says (roughly) “wake up!” This causes the machine to power ON and boot into the operating system environment. This is the theory. Unfortunately, some times things don't work as they are supposed to.

Symptoms ^

Powered-off clients do not respond to WOL “wake-up” requests
Clients which are often powered-off are not getting Advertisements or Updates

Potential causes ^

Incorrect Client Agent settings
Firewall port exceptions
Router and Switch configuration settings
Client BIOS firmware, or driver compatibility issues

Suggestions ^

It’s important to understand that WOL is not simply a matter of configuring clients and servers. The network layer is a vital component in the overall process. In many environments, routers and switches are not configured to allow WOL to work between LAN segments. Make sure the appropriate ports are opened and that everything is configured in accordance with standard guidelines.

I like to emphasize “patterns” when performing any troubleshooting effort. For example, if you find only specific computers within a given LAN segment are not responding to WOL requests, it doesn’t likely point to a network (switch or router) configuration issue. That would usually point to machine-specific issues, such as BIOS settings, firmware capability, and drivers. However, it could also point to bad network cabling or bad connectors.

If it appears that all computers on a given LAN segment are not responding, then I would suggest looking at the routers or switches which serve those computers.
If the computers are in Active Directory OU locations which share common Group Policy Object links, check for common/unique Group Policy settings as well.
Verify Configuration Manager Client Agent settings.
Verify Clients are getting policy updates and are reporting discovery and inventory data properly.