Network is corrupted between Guest OS and external network for VMs hosted on Windows 8.1 or Windows Server 2012 R2

View products that this article applies to.

This article describes an issue in which the network traffic is corrupted between Guest OS and the external network for virtual machines (VMs) that are hosted on Windows 8.1 or Windows Server 2012 R2. A hotfix is available to fix this issue. Before you install this hotfix, see the Prerequisites section.

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Symptoms

This issue occurs when you route traffic from a VM network adapter to another VM or host network adapter, and when Large Send Offload (LSO) v2 is enabled on the VM network adapter.

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Cause

This issue occurs because the VM switch may not set LSO information correctly when outgoing packets are forwarded between VM and host network adapters.

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Hotfix information

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

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that's described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there's a "Hotfix Download Available" section at the top of this Knowledge Base article. If this section doesn't appear, submit a request to Microsoft Customer Service and Support to get the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that don't qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft website:

http://support.microsoft.com/contactus/?ws=support

Note The "Hotfix Download Available" form displays the languages for which the hotfix is available. If you don't see your language, it's because a hotfix isn't available for that language.

Prerequisites

To apply this hotfix, install update 2919355 in Windows 8.1 or Windows Server 2012 R2.

Registry information

To use the hotfix in this package, you don't have to make any changes to the registry.

Restart requirement

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

Hotfix replacement information

This hotfix doesn't replace a previously released hotfix.

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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 8.1 and Windows Server 2012 R2

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 0.17 xxx Windows 8.1 and Windows Server 2012 R2 RTM GDR
6.3.960 0.18 xxx Windows 8.1 and 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.

Version	Product	Milestone	Service branch
6.3.960 0.17 xxx	Windows 8.1 and Windows Server 2012 R2	RTM	GDR
6.3.960 0.18 xxx	Windows 8.1 and Windows Server 2012 R2	RTM	GDR

x64 Windows 8.1 and Windows Server 2012 R2

File name	File version	File size	Date	Time	Platform
Vmsif.dll	6.3.9600.17396	65,024	08-Oct-2014	05:53	x64
Vmsnetsetupplugin.dll	6.3.9600.17396	33,792	08-Oct-2014	06:07	x64
Vmswitch.sys	6.3.9600.18086	689,152	08-Oct-2015	17:33	x64
Vmsif.dll	6.3.9600.17396	65,024	08-Oct-2014	05:53	x64
Vmsntfy.dll	6.3.9600.17396	91,648	08-Oct-2014	06:54	x64
Vmswitch.sys	6.3.9600.18086	689,152	08-Oct-2015	17:33	x64
Vmsif.dll	6.3.9600.17396	65,024	08-Oct-2014	05:53	x64
Vmsntfy.dll	6.3.9600.17396	91,648	08-Oct-2014	06:54	x64
Vmswitch.sys	6.3.9600.18086	689,152	08-Oct-2015	17:33	x64
Vmsif.dll	6.3.9600.17396	65,024	08-Oct-2014	05:53	x64
Vmsntfy.dll	6.3.9600.17396	91,648	08-Oct-2014	06:54	x64
Vmswitch.sys	6.3.9600.18086	689,152	08-Oct-2015	17:33	x64

Additional file information

x64 Windows 8.1 and Windows Server 2012 R2

File property	Value
File name	Amd64_0140230e6202200b304391ecea98411a_31bf3856ad364e35_6.3.9600.18086_none_b2b7e84f9ca1bf41.manifest
File version	Not applicable
File size	725
Date (UTC)	09-Oct-2015
Time (UTC)	12:49
Platform	Not applicable

File name	Amd64_4a257e5b81b15fc83d9132c5e0ea7dd6_31bf3856ad364e35_6.3.9600.18086_none_41877c9067678c6b.manifest
File version	Not applicable
File size	708
Date (UTC)	09-Oct-2015
Time (UTC)	12:49
Platform	Not applicable

File name	Amd64_microsoft-hyper-v-d..ch-coresystem-state_31bf3856ad364e35_6.3.9600.18086_none_e855ef6e438e902f.manifest
File version	Not applicable
File size	10,027
Date (UTC)	09-Oct-2015
Time (UTC)	12:49
Platform	Not applicable

File name	Amd64_microsoft-hyper-v-drivers-vmswitch_31bf3856ad364e35_6.3.9600.18086_none_59cb66e054125d60.manifest
File version	Not applicable
File size	7,613
Date (UTC)	09-Oct-2015
Time (UTC)	12:49
Platform	Not applicable

File name	Amd64_wvms_pp.inf_31bf3856ad364e35_6.3.9600.18086_none_53a5c0bac557d654.manifest
File version	Not applicable
File size	3,379
Date (UTC)	09-Oct-2015
Time (UTC)	12:49
Platform	Not applicable

File name	Amd64_wvms_pp_coresys.inf_31bf3856ad364e35_6.3.9600.18086_none_6223d3fd6046e683.manifest
File version	Not applicable
File size	3,411
Date (UTC)	09-Oct-2015
Time (UTC)	12:49
Platform	Not applicable

File name	Update.mum
File version	Not applicable
File size	2,737
Date (UTC)	09-Oct-2015
Time (UTC)	12:49
Platform	Not applicable