NLB cluster communication gets interrupted when MAC impersonation security feature is enabled in Windows Server 2012 R2

This article describes a problem in which Network Load Balancing (NLB) cluster communication gets interrupted randomly in Windows Server 2012 R2. An update is available to fix this problem. Before you install this update, see the Prerequisites section.
This problem occurs when a security feature is enabled in your environment to prevent MAC impersonation and when an NLB cluster is set to operate in Internet Group Management Protocol (IGMP) multicast mode. In this configuration, the IGMPv1 multicast membership reports are randomly sent by having an incorrect source MAC address. This situation interferes with the security settings of the intermediate devices that are used, and this breaks the cluster communication.

How to get this update
Important If you install a language pack after you install this update, you must reinstall this update. Therefore, we recommend that you install any language packs that you need before you install this update. For more information, see Add language packs to Windows.

Method 1: Windows Update

This update is provided as a Recommended update on Windows Update. For more information on how to run Windows Update, see How to get an update through Windows Update.

Method 2: Microsoft Download Center

The following files are available for download from the Microsoft Download Center.
Operating systemUpdate
All supported x64-based versions of Windows Server 2012 R2DownloadDownload the package now.
For more information about how to download Microsoft support files, select the following article number to view the article in the Microsoft Knowledge Base:
119591 How to obtain Microsoft support files from online services
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.
Update detail information


To install this update, install April 2014, update rollup for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 (2919355) in Windows Server 2012 R2.

Registry information

To apply this update, you don't have to make any changes to the registry.

Restart requirement

You may have to restart the computer after you apply this update.

Update replacement information

This update doesn't replace a previously released update.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminology that Microsoft uses to describe software updates.
File Information
The English (United States) version of this software update installs files that have the attributes that are listed in the following tables. The dates and times for these files are listed in Coordinated Universal Time (UTC). Be aware that dates and times for these files on your local computer are displayed in your local time and with your current daylight saving time bias. The dates and times may also change when you perform certain operations on the files.

Windows Server 2012 R2

  • The files that apply to a specific product, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table.

    VersionProductMilestoneService branch
    6.3.960 0.18xxxWindows Server 2012 R2RTMGDR
  • GDR service branches contain only those fixes that are widely released to address widespread, critical issues. LDR service branches contain hotfixes in addition to widely released fixes.
  • The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed in the "Additional file information" section. MUM, MANIFEST, and the associated security catalog (.cat) files, are very important to maintain the state of the updated components. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.
x64 Windows 8.1 and Windows Server 2012 R2
File nameFile versionFile sizeDateTimePlatform

Additional file information

x64 Windows 8.1 and Windows Server 2012 R2
File propertyValue
File nameAmd64_14b74b7fe21f0785a6fabecb2fc2f364_31bf3856ad364e35_6.3.9600.18185_none_b9a15354fdd295a3.manifest
File versionNot applicable
File size726
Date (UTC)30-Dec-2015
Time (UTC)23:19
PlatformNot applicable
File nameAmd64_microsoft-windows-n..ncing-networkdriver_31bf3856ad364e35_6.3.9600.18185_none_9ec926d2ec60505f.manifest
File versionNot applicable
File size2,708
Date (UTC)30-Dec-2015
Time (UTC)15:34
PlatformNot applicable
File nameUpdate.mum
File versionNot applicable
File size1,599
Date (UTC)30-Dec-2015
Time (UTC)23:19
PlatformNot applicable
Note This is a "FAST PUBLISH" article created directly from within the Microsoft support organization. The information contained herein is provided as-is in response to emerging issues. As a result of the speed in making it available, the materials may include typographical errors and may be revised at any time without notice. See Terms of Use for other considerations.

Article ID: 3130934 - Last Review: 03/08/2016 18:56:00 - Revision: 3.0

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