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

Leave a Reply


Nick Kelly

Cybersecurity Engineer, Cisco

Nick has over 20 years of experience in Security Operations and Security Sales. He is an avid student of cybersecurity and regularly engages with the Infosec community at events like BSides, RVASec, Derbycon and more. The son of an FBI forensics director, Nick holds a B.S. in Criminal Justice and is one of Cisco’s Fire Jumper Elite members. When he’s not working, he writes cyberpunk and punches aliens on his Playstation.


Virgilio “BONG” dela Cruz Jr.

CCDP, CCNA V, CCNP, Cisco IPS Express Security for AM/EE
Field Solutions Architect, Tech Data

Virgilio “Bong” has sixteen years of professional experience in IT industry from academe, technical and customer support, pre-sales, post sales, project management, training and enablement. He has worked in Cisco Technical Assistance Center (TAC) as a member of the WAN and LAN Switching team. Bong now works for Tech Data as the Field Solutions Architect with a focus on Cisco Security and holds a few Cisco certifications including Fire Jumper Elite.


John Cavanaugh

CCIE #1066, CCDE #20070002, CCAr
Chief Technology Officer, Practice Lead Security Services, NetCraftsmen

John is our CTO and the practice lead for a talented team of consultants focused on designing and delivering scalable and secure infrastructure solutions to customers across multiple industry verticals and technologies. Previously he has held several positions including Executive Director/Chief Architect for Global Network Services at JPMorgan Chase. In that capacity, he led a team managing network architecture and services.  Prior to his role at JPMorgan Chase, John was a Distinguished Engineer at Cisco working across a number of verticals including Higher Education, Finance, Retail, Government, and Health Care.

He is an expert in working with groups to identify business needs, and align technology strategies to enable business strategies, building in agility and scalability to allow for future changes. John is experienced in the architecture and design of highly available, secure, network infrastructure and data centers, and has worked on projects worldwide. He has worked in both the business and regulatory environments for the design and deployment of complex IT infrastructures.