This article describes an issue that occurs when you use load balancing and failover (LBFO) Dynamic Teaming in Windows Server 2012 R2. You can fix this issue by using the update in this article. Before you install this update, see the Prerequisites section.

Symptoms

Windows Server 2012 R2 server may drop packets if the following settings are configured:

  • Network Interface Card (NIC) Teaming is enabled.

  • Teaming Load Balancing Mode: Dynamic.

  • More than one NIC is in Active Mode.

When packet dropping occurs, event ID 8 is logged in Event Viewer under Applications and Services Logs > Microsoft > MsLbfoProvider > Operational view that looks something like this: Therefore, you may encounter the following issues but not limit to these issues:

  • Cluster nodes are unexpectedly removed from cluster groups.

  • SQL database transaction failures.

  • TCP connection stops.

Cause

This issue occurs because a race condition causes NIC Teaming Dynamic load balance algorithm to drop packets.

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 update is available for download from the Microsoft Download Center:

Download Download the Windows Server 2012 R2 package now.

For more information about how to download Microsoft support files, click 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

Prerequisites

To apply this update, you must have April 2014 update rollup for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 (2919355) installed 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.

Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information

Dynamic teaming load balancing is a new feature in Windows Server 2012 R2. Windows Server 2012 R2 servers default to dynamic mode when teaming NICs are created on physical computers. LBFO driver versions earlier than this KB 3137691 may incorrectly drop packets. Such packet loss can increase as processor cores are added and network traffic increases.

References

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.

Notes

  • 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:

    Version

    Product

    Milestone

    Service branch

    6.3.960 0.18 xxx

    Windows Server 2012 R2

    RTM

    GDR

  • 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 Server 2012 R2

File name

File version

File size

Date

Time

Platform

Mslbfoprovider.sys

6.3.9600.18203

117,248

20-Jan-2016

14:52

x64


x64 Windows Server 2012 R2

File property

Value

File name

Amd64_6d6688b652458c5bc8235e5e12e0dbe7_31bf3856ad364e35_6.3.9600.18203_none_d736a0b83ae7a769.manifest

File version

Not applicable

File size

701

Date (UTC)

21-Jan-2016

Time (UTC)

22:07

Platform

Not applicable

File name

Amd64_microsoft-windows-ndis-lbfo_31bf3856ad364e35_6.3.9600.18203_none_0277b04fea8819a8.manifest

File version

Not applicable

File size

21,621

Date (UTC)

20-Jan-2016

Time (UTC)

15:45

Platform

Not applicable

File name

Update.mum

File version

Not applicable

File size

1,839

Date (UTC)

21-Jan-2016

Time (UTC)

22:07

Platform

Not applicable


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