After you install Microsoft Windows Server 2003 Service Pack 2 (SP2) or Microsoft Windows Server 2003 Scalable Networking Pack on a Microsoft Windows Server 2003-based computer, you may experience many network-related symptoms.

These symptoms may include one or more of the following:

•	When you try to connect to the server by using a VPN connection, you receive the following error message: Error 800: Unable to establish connection.
•	You cannot create a Remote Desktop Protocol (RDP) connection to the server.
•	You cannot connect to shares on the server from a computer on the local area network.
•	You cannot join a client computer to the domain.
•	You cannot connect to Microsoft Exchange Server from a computer that is running Microsoft Outlook.
•	You can only connect to Web sites that are hosted on the server or on the Internet by using a secure sockets layer (SSL) connection. In this scenario, you cannot connect to a Web site that does not use SSL encryption.
•	You experience slow network performance.
•	You cannot create an outgoing FTP connection from the server.
•	The DHCP Server service crashes.
•	Clients experience slow domain logons.
•	Network Address Translation (NAT) clients that are located behind Windows SBS 2003 experience intermittent connection failures.
•	You experience intermittent RPC communications failures.
•	Clients that are configured as SecureNat clients may be unable to connect to the Internet.
•	Some Outlook clients may be unable to connect to Exchange.
•	You cannot run the Configure E-mail and Internet Connection Wizard successfully.
•	Microsoft Internet Security and Acceleration (ISA) Server blocks RPC communications.
•	Clients cannot visit the http://companyweb Web site.
•	You cannot browse Internet Information Services (IIS) Virtual Directories.

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This problem occurs because of a problem that exists in NAT in Windows Server 2003. This problem is exposed when you enable one of the following features on a network adapter that meets the NDIS 5.2 specification or a later version of this specification:

•	Receive Side Scaling (RSS)
•	TCP/IP offloading

Windows Server 2003 SP2 and the Windows Server 2003 Scalable Networking Pack include features to implement stateful and stateless offloading. The offloading feature accelerates the Windows networking stack. The networking update that is included in Windows Server 2003 SP2 and in the Windows Server 2003 Scalable Networking Pack includes the following features:

•	TCP Chimney Offload
•	Receive Side Scaling
•	Network Direct Memory Access (NetDMA)

A problem exists that affects NAT when you have Receive Side Scaling enabled. Therefore, after you install Windows Server 2003 SP2 or the Windows Server 2003 Scalable Networking Pack on a computer, you experience the symptoms that are mentioned in the "Symptoms" section.

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The following file is available for download from the Microsoft Download Center:

Download the 948496 package now. (http://www.microsoft.com/downloads/details.aspx?FamilyId=062E954C-FDEC-45AF-A09C-5A05B8F010A5)

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base: 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.

If you are running Windows Small Business Server 2003 with Windows Server 2003 Service Pack 2, you can obtain this update from Microsoft Update. To download the service pack from Microsoft Update, visit the following Microsoft Web site: Note The update that is described in this article may also resolve issues that may occur in Windows Compute Cluster Server 2003 after you install Windows Server 2003 Service Pack 2 or after you install the Scalable Networking Pack.

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To work around this problem, follow these steps.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

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Step 1: Install the latest updates for Microsoft Internet Security and Acceleration (ISA) Server 2004

If you are running ISA Server 2004 in Windows Server 2003, install the latest ISA Server 2004 updates. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

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Step 2: Update the network adapter drivers

Contact the network adapter manufacturer or contact the original equipment manager (OEM) for the computer to determine whether an updated network adapter driver is available. You must have drivers that are compatible with NDIS 5.2 or with a later version. If you still experience the problem that is mentioned in this article after you install the latest network adapter driver, continue to "Step 3: Disable Receive Side Scaling."

For information about how to contact computer hardware manufacturers, click the appropriate article number in the following list to view the article in the Microsoft Knowledge Base:

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Step 3: Disable Receive Side Scaling

Disable Receive Side Scaling on the server. To do this, use one of the following methods.

Method 1: Modify the network adapter properties to disable Receive Side Scaling

1.	Click Start, click Run, type ncpa.cpl, and then click OK.
2.	Right-click a network adapter object, and then click Properties.
3.	Click Configure, and then click the Advanced tab.
4.	In the Property list, click Receive Side Scaling, click Disable in the Value list, and then click OK.
5.	Repeat steps 2 through 4 for each network adapter object.

Method 2: Modify the registry to disable Receive Side Scaling

1.	Click Start, click Run, type regedit, and then click OK.
2.	Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3.	If the EnableRSS registry entry does not exist, create it. To do this, follow these steps: a. On the Edit menu, point to New, and then click DWORD Value. b. In the New Value #1 box, type EnableRSS, and then press ENTER.
4.	Right-click EnableRSS, and then click Modify.
5.	In the Value data box, type 0 (zero), and then click OK.
6.	Exit Registry Editor.

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Step 4: Disable offloading support

1.	Click Start, click Run, type regedit, and then click OK.
2.	Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3.	In the details pane, right-click EnableTCPA, and then click Modify. Note If the EnableTCPA registry entry does not exist, create it. To do this, follow these steps: a. On the Edit menu, point to New, and then click DWORD Value. b. In the New Value #1 box, type EnableTCPA, and then press ENTER.
4.	In the Value data box, type 0 (zero), and then click OK.
5.	Exit Registry Editor.
6.	Restart the computer.

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

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For more information about how to troubleshoot networking issues that you may experience with Windows Small Business Server 2003, click the following article number to view the article in the Microsoft Knowledge Base: For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base: For more information about the Windows Server 2003 Scalable Networking Pack, visit the following Microsoft Web site: For more information about this problem in Windows Small Business Server, visit the following Microsoft Web log (blog) site:

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