An IPv6 readiness update is available for Windows 7 and for Windows Server 2008 R2

Issues that are fixed in this update

Issue 1

When you assign a public IPv4 address in an environment, 6to4 addresses are automatically assigned to the servers and clients computers. This behavior is by default and occurs even when the computer does not have an E2E IPv6 connection or a 6to4 connection. Therefore, you may be unable to connect to IPv6 sites.

Note The expected behavior is that Windows clients do not assign 6to4 addresses unless the connection is confirmed.

This update enables Windows to check whether the relay can be reached before Windows adds a route to it. Windows deletes the route if the connection to the relay is unavailable. This behavior prevents Windows from trying to connect to an IPv6 address that cannot be reached through the relay.

Note The relay is the 6to4 public route that the 6to4 packet uses to reach its destination.

Issue 2

If you use many IPv6 address and IPv6 routes, the kernel memory is exhausted, and CPU usage reaches 100 percent.

This update limits the number of advertised prefixes and routes that each interface can process to 100.

Issue 3

If a computer has a public IPv4 address and if Internet Connection Sharing is enabled, the computer broadcasts a router advertisement (RA) message for the 6to4 address that is generated. Therefore, other computers are assigned IPv6 addresses. This behavior disconnects these computers if the computer that broadcasts the 6to4 RA does not have an E2E 6to4 connection.

Note Because of recommendations in the RFC 6343 document, you cannot disable 6to4 sharing.

After this update is installed, the automatic Connection Sharing 6to4 sharing functionality in Windows is disabled by default.

Issue 4

Assume that a computer is configured to use an IPv6 connection as the default connection. Additionally, assume that the computer does not have a connection to an IPv6 network. In this situation, it takes a long time for the computer to connect to an IPv6 site. 

This issue occurs because Windows tries the IPv6 connection first. After the connection fails because of a time-out error, Windows tries the IPv4 connection.

After this update is installed, Windows uses the NCSI functionality to examine the Ipv6 connection. If the connection is broken, Windows uses IPv4 instead of IPv6.

Update information

Windows Update

This update is available from Windows Update.

Microsoft Download Center

The following files are available for download from the Microsoft Download Center:
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.

Prerequisites

To apply this update, you must be running Windows 7 Service Pack 1 (SP1) or Windows Server 2008 R2 Service Pack 1 (SP1).

Registry information

To apply this update, you do not have to make any changes to the registry.

Restart requirement

You must restart the computer after you apply this update.

Hotfix replacement information

This update does not replace a previously released update.

File information

The global version of this update installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.

Windows 7 and Windows Server 2008 R2 file information 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
  6.1.760 1.17xxx	Windows 7 and Windows Server 2008 R2	SP1	GDR
  6.1.760 1.22xxx	Windows 7 and Windows Server 2008 R2	SP1	LDR

• 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 separately in the "Additional file information for Windows 7 and for Windows Server 2008 R2" section. MUM and MANIFEST files, and the associated security catalog (.cat) files, are critical to maintaining the state of the updated component. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates