Microsoft WSUS Guide for Cisco NAC Deployments


There are a number of benefits for using a WSUS server. Some of the benefits are

  • Control when updates are installed – This allows companies to test updates before deploying them to the user community.
  • Lower internet bandwidth usage – Keep the bandwidth, used for downloading Microsoft updates, within the internal network. This would keep the internet connection from becoming overloaded by users downloading updates directly from Microsoft

From a security perspective, keeping current with the latest Microsoft updates is very important. Computers are vulnerable to attacks if they do not have they do not have the latest security updates installed. Cisco NAC can make sure computers have approved Microsoft updates by using a WSUS Requirement. This requirement uses the WSUS API, on the the end computer, to poll the WSUS server for an index of all approved Microsoft updates. The end computer then uses the local Windows Update Agent to compare the local index, called a data store, with the index received from the WSUS server. Any differences would cause the Cisco NAC remediation dialog box to appear and guide the end user through downloading and installing the Microsoft updates.

In theory this should be a seamless process that occurs quickly. In practice, there are a number of problems that can occur. Some common problems are problems connecting to the WSUS server and errors when connecting to the WSUS server. Below are some common tools to use for troubleshooting WSUS problems.

Common Troubleshooting Tools

  1. wuauclt.exe /detectnow – This is a great command to initiate detection of the WSUS server manually. Without this command you need to wait for the Automatic Update process to kick off.
  2. c:WINDOWSWindowsUpdate.log – This file provides invaluable logs regarding the status of the Windows update progress.
  3. esentutl.exe – This command is a database utility that can recover and repair the database used, on the end computer. The database is stored in c:WINDOWSSoftwareDistributionDataStoreDataStore.edb
  4. WSUS Client Diagnostics Tool – This tool checks the basic settings required for WSUS to work. The link above provides access to the Microsoft website providing more information about the tool along with a link to download

Here’s an example on how the first two tools would be used.

A user is having problems getting Microsoft updates from the WSUS server. You go to the users computer and check out the c:WINDOWSwindowsupdate.log file. In the file, you notice the following error message

WARNING: WU client failed Searching for update with error 0x8024400e

You run “wuauclt.exe /detectnow” and check the windowsupdate.log file again to make sure the problem is still occurring. After verifying that it still occurring, you do a Google search on “error 0x8024400e” and find a link to a website describing a similar problem and offering a solution. You contact the WSUS team and have them implement the change to fix the problem.

While Google searches are excellent ways of obtaining information about WSUS, I’ve found a number of links to start your troubleshooting efforts with. Below are the best links I’ve found to start your research

    1. Main Microsoft WSUS Site including Configuration Guides
    2. Free Microsoft Support
    3. WSUS Wiki Site
    4. How to read the WindowsUpdate.log File
    5. Microsoft Blog about WSUS
    6. WSUS Forum
    7. WindowsUpdate Posts on
    8. Microsoft WSUS Discussion Group

Posted by Rob Chee at 9:29 AM

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