Some network connections do not work after you connect a PPP-based network interface in Windows Server 2008 R2 or in Windows 7

Consider the following scenario:

• You install two network adapters on a computer that is running Windows Server 2008 R2 or Windows 7.
• These two network adapters connect to two networks. For example, one network adapter connects to the Internet and the other network adapter connects to the intranet.
• You create a Point-to-Point Protocol (PPP)-based network interface on the computer. For example, you create a Point-to-Point Protocol�over Ethernet (PPPoE) interface, a dial-up interface, or a VPN interface on the computer.
• You configure the PPP-based network interface to connect to the same network to which one of the other network adapters connects. For example, you configure the PPP-based network interface to connect to the Internet.
• IP routing is enabled on the network interfaces.
• You connect the PPP-based network interface to its network.

In this scenario, some network connections do not work.

For example, consider the following scenario:

• You have three network interfaces (A, B, and C) on a computer that is running Windows Server 2008 R2. IP routing is enabled on these interfaces.
• Interface A connects to a corporate network.
• Interface B connects to the Internet.
• Interface C is PPP-based and is also configured to connect to the Internet.
• You access the computer from a remote computer by using network interface B.
• You connect to the Internet by using interface C.

In this scenario, you can no longer access the computer from the remote computer.

This issue occurs because the default gateway causes the default route to be changed to the PPP-based connection when the connection is engaged. This behavior redirects the outgoing communication to the remote computer so that it flows over the PPP-based connection when the incoming communication stays on the Internet-facing interface. The PPP framing layer driver drops these outgoing packets on the PPP-based interface when the packet-spoofing protection mechanism is enabled.

The following hotfix gives you the option of disabling the packet-spoofing protection mechanism.

Note�The packet-spoofing drop is given for security reasons. You must understand well the implications of disabling the packet-spoofing protection mechanism.

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain 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 do not 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: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

To apply this hotfix, you must be running one of the following operating systems:

• Windows 7
• Windows 7 Service Pack 1 (SP1)
• Windows Server 2008 R2
• Windows Server 2008 R2 SP1

For more information about how to obtain a Windows 7 or a Windows Server 2008 R2 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

Registry information

After apply this hotfix, you must create a registry key. To do this, follow these steps:

1. Click Start
   , type regedit in the Search programs and files�box, and then press Enter.�
   If you are prompted for an administrator password, type the password. If you are prompted for confirmation, provide confirmation.
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\WANARP6\Parameters
3. On the Edit menu, point to New, and then click DWORD (32-bit) Value.
4. Type DisableSpoofingProtection, and then press Enter.�
5. Right-click DisableSpoofingProtection, and then click Modify.
6. In the Value data box, type 1, and then click OK.
7. Exit Registry Editor.

Note If the value of the registry key is 0, or if the registry key does not exist, no change is applied, and the packet-spoofing protection mechanism is enabled. If the value of the registry key is�1, the packet-spoofing protection mechanism is disabled, and the issue is resolved.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

File information

The global version of this hotfix 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

Important Windows 7 hotfixes and Windows Server 2008 R2 hotfixes are included in the same packages. However, hotfixes on the Hotfix Request page are listed under both operating systems. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows 7/Windows Server 2008 R2" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.

• 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 0.16xxx	Windows 7 and Windows Server 2008 R2	RTM	GDR
  6.1.760 0.20xxx	Windows 7 and Windows Server 2008 R2	RTM	LDR
  6.1.760 1.17xxx	Windows 7 and Windows Server 2008 R2	SP1	GDR
  6.1.760 1.21xxx	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 all supported x86-based versions of Windows 7

For all supported x64-based versions of Windows 7 and of Windows Server 2008 R2

For all supported IA-64-based versions of Windows Server 2008 R2

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

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

Additional file information

Additional file information for Windows 7 and for Windows Server 2008 R2

Additional files for all supported x86-based versions of Windows 7

Additional files for all supported x64-based versions of Windows 7 and of Windows Server 2008 R2

Additional files for all supported IA-64-based versions of Windows Server 2008 R2