How to Enable Unknown Computer Support for a PXE Service Point

System Center

Updated: October 28, 2009

Applies To: System Center Configuration Manager 2007, System Center Configuration Manager 2007 R2, System Center Configuration Manager 2007 R3, System Center Configuration Manager 2007 SP1, System Center Configuration Manager 2007 SP2

In Microsoft System Center Configuration Manager 2007, you set the operating system deployment PXE service point response to incoming PXE requests from unknown computers by setting the SupportUnknownMachines embedded property.

SupportUnknownMachines has the following possible values.


Value Description


The PXE service point does not respond to PXE requests from unknown computers.


The PXE service point responds to requests from unknown computers.

To set the PXE service point response to PXE requests from unknown computers

  1. Set up a connection to the SMS Provider. For more information, see About the SMS Provider in Configuration Manager.

  2. Make a connection to the PXE service point resources section of the site control file.

  3. Get the embedded properties.

  4. Update the SupportUnknownMachines embedded property.

  5. Commit the changes to the site control file.


The following example method sets the response for a PXE request based on the supplied Boolean value (allowResponse).

For information about calling the sample code, see Calling Configuration Manager Code Snippets.

public void SetUnknownComputerSupport(
    WqlConnectionManager connection, 
    string server, 
    string siteCode,
    bool respondToUnknownMachines)
        // Get PXE properties.
        IResultObject ro = connection.GetInstance("SMS_SCI_SysResUse.FileType=2,ItemName='[\"Display=\\\\" + server + "\\\"]MSWNET:[\"SMS_SITE=" + siteCode + "\"]\\\\" + server + "\\,SMS PXE Service Point',ItemType='System Resource Usage',SiteCode='" + siteCode + "'");

        Dictionary<string, IResultObject> embeddedProperties = ro.EmbeddedProperties; // Get a copy

        embeddedProperties["SupportUnknownMachines"]["Value"].BooleanValue = respondToUnknownMachines;

        ro.EmbeddedProperties = embeddedProperties;
    catch (SmsException e)
        Console.WriteLine("Failed to set unknown machine support on PXE Service point: " + e.Message);

Sub SetUnknownComputerSupport(connection,          _
                     context,           _
                     siteCode,               _
    ' Load site control file and get SMS PXE service point section.
    connection.ExecMethod "SMS_SiteControlFile.Filetype=1,Sitecode=""" & siteCode & """", "Refresh", , , context
    Query = "SELECT * FROM SMS_SCI_SysResUse " & _
            "WHERE RoleName = 'SMS PXE Service Point' " & _
            "AND SiteCode = '" & siteCode & "'"
    Set SCIComponentSet = connection.ExecQuery(Query, ,  , context)
    ' Only one instance is returned from the query.
    For Each SCIComponent In SCIComponentSet

         ' Display SMS PXE service point server name.
         wscript.echo "SMS PXE Service Point Server: " & SCIComponent.NetworkOSPath                                    
        ' Loop through the array of embedded property instances.
        For Each vProperty In SCIComponent.Props
            ' Setting: IsActive
            If vProperty.PropertyName = "SupportUnknownMachines" Then
                wscript.echo " "
                wscript.echo vProperty.PropertyName
                wscript.echo "Current value " &  vProperty.Value               
                ' Modify the value.
                vProperty.Value = respondToUnknownMachines
                wscript.echo "New value " & respondToUnknownMachines
            End If

             ' Update the component in your copy of the site control file. Get the path
             ' to the updated object, which could be used later to retrieve the instance.
             Set SCICompPath = SCIComponent.Put_( , context)
    ' Commit the change to the actual site control file.
    Set InParams = connection.Get("SMS_SiteControlFile").Methods_("CommitSCF").InParameters.SpawnInstance_
    InParams.SiteCode = siteCode
    connection.ExecMethod "SMS_SiteControlFile", "CommitSCF", InParams, , context
End Sub

The example method has the following parameters:






  • Managed: WqlConnectionManager

  • VBScript: SWbemServices

A valid connection to the SMS Provider.

context (VBScript)

  • VBScript: SWbemContext

A valid context object. For more information, see How to Add a Configuration Manager Context Qualifier by Using WMI.


  • Managed: String

The Configuration Manager server.


  • Managed: String

  • VBScript: String

The Configuration Manager site code.


  • Managed: Boolean

  • VBScript: Boolean

The response type.

true if the PXE service point responds to PXE requests; otherwise false.

Compiling the Code

The C# example has the following compilation requirements:










Robust Programming

For more information about error handling, see About Configuration Manager Errors.


For more information about securing Configuration Manager applications, see About Securing Configuration Manager Applications.

See Also