Microsoft KB Archive/900256

= Error message when ISA Server 2004 Web Proxy client users try to access an external FTP site by using passive FTP functionality: &quot;Error Code: 502 Proxy Error&quot; =

Article ID: 900256

Article Last Modified on 12/4/2007

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APPLIES TO


 * Microsoft Internet Security and Acceleration Server 2004 Enterprise Edition
 * Microsoft Internet Security and Acceleration Server 2004 Standard Edition

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Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry



SYMPTOMS
Consider the following scenario:
 * You configure Microsoft Internet Security and Acceleration (ISA) Server 2004 to enable outgoing passive FTP traffic.
 * You configure several internal client computers as ISA Server 2004 Web Proxy clients.

In this scenario, the internal Web Proxy clients can at first access external FTP sites and external Web sites. However, after several days or more, users receive the following error message when they use a Web Proxy client to access an external FTP site or an external Web site:

Error Code: 502 Proxy Error. No buffer space is supported.

The WinSock implementation was unable to allocate additional memory to accommodate the function request. (10055)

Note You experience this problem only if the values for the  registry subkey are set as follows on the computer that is running ISA Server 2004:

Value name: NonPassiveFTPTransfer

Value data: 0x0



CAUSE
When ISA Server 2004 is configured in the manner that is described in the &quot;Symptoms&quot; section, ISA Server 2004 leaks socket endpoint handles. Specifically, ISA Server 2004 leaks a handle every time that a file is downloaded from an external FTP server.



Service pack information
To resolve this problem, obtain the latest service pack for Internet Security and Acceleration Server 2004. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

891024 How to obtain the latest ISA Server 2004 service pack

Service pack information
To resolve this problem, obtain ISA Server 2004, Standard Edition Service Pack 2 (SP2). For more information, click the following article number to view the article in the Microsoft Knowledge Base:

891024 How to obtain the latest ISA Server 2004 service pack

Service pack information
To resolve this problem, obtain ISA Server 2004, Enterprise Edition Service Pack 2 (SP2). For more information, click the following article number to view the article in the Microsoft Knowledge Base:

891024 How to obtain the latest ISA Server 2004 service pack

Hotfix information
A supported hotfix is now 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 this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next service pack that contains this hotfix.

To resolve this problem, submit a request to Microsoft Online Customer Services to obtain the hotfix. To submit an online request to obtain the hotfix, visit the following Microsoft Web site:

http://go.microsoft.com/?linkid=6294451

Note If additional issues occur or 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. To create a separate service request, visit the following Microsoft Web site:

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

Prerequisites
You must be running ISA Server 2004 Enterprise Edition to install this hotfix. You cannot install this hotfix on a computer that is running ISA Server 2004 Standard Edition.

Restart requirement
You do not have to restart your computer after you apply this hotfix. However, ISA Server 2004-related services are automatically stopped and then restarted when you apply this hotfix.

Hotfix replacement information
This hotfix does not replace any other hotfixes.

File information
The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.



WORKAROUND
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk. To work around this problem, disable passive FTP functionality in ISA Server 2004. To do this, set the following values on the  subkey:

Value name: NonPassiveFTPTransfer

Value type: REG_DWORD

Value data: 0x1

Note After you configure this registry entry, you must restart the ISA Server 2004 Firewall service for this change to take effect.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section. This problem was first corrected in ISA Server 2004 Service Pack 2. This problem was first corrected in Internet Security and Acceleration Server 2004 Service Pack 2.



MORE INFORMATION
For more information about how to install ISA Server 2004 hotfixes and updates, click the following article number to view the article in the Microsoft Knowledge Base:

885957 How to install ISA Server hotfixes and updates

For more information about the terms that are used in this article, 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

Keywords: kbbug kbfix kbqfe kbpubtypekc kbhotfixserver KB900256

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