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Q193891: HTTP Through Firewall and "Bypass Proxy for Local Intranet"

Article: Q193891
Product(s): Microsoft Windows NT
Version(s): WinNT:4.0,4.0a
Operating System(s): 
Keyword(s): kbWinNT400sp4fix
Last Modified: 10-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Server version 4.0 
- Microsoft Windows NT Workstation version 4.0 
- Microsoft Windows NT Server, Enterprise Edition version 4.0 
- Microsoft Windows NT Server version 4.0, Terminal Server Edition 
- Microsoft BackOffice Small Business Server versions 4.0, 4.0a 
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SYMPTOMS
========

"Bypass proxy server for local (Intranet) addresses" may not work as expected.

When a client process attempts to connect to an Internet address (for example,
www.microsoft.com) through a proxy server when the above setting is selected,
the first call to tcp_get_host_by_name uses that Internet server name
(www.microsoft.com) as the server. Next, RPC sets up the tunneling, the proxy
server redirects the call to the real server (www.microsoft.com), the response
packet comes back to the proxy, the proxy redirects it back to the client, and
the client sends it to the client process. However, the response packet contains
the actual IP address of the Internet server. The client thinks that there is no
proxy server and attempts to communicate directly to the Internet IP address
that is unreachable; therefore, the connection fails.

If the "Bypass proxy server for local (intranet) addresses" setting is not
selected, the call is always directed to the http proxy; however, if you do not
select it, you may not be able to communicate or connect to Intranet servers.

CAUSE
=====

The problem is that, if tcp_get_host_by_name() passes an address instead of a
server name, it needs to force a name resolution to make sure the host is
reachable.

RESOLUTION
==========

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or
Windows NT Server 4.0, Terminal Server Edition. For additional information,
please see the following article in the Microsoft Knowledge Base:

  Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack



STATUS
======

Microsoft has confirmed this to be a problem in Windows NT 4.0 and Windows NT
Server 4.0, Terminal Server Edition. This problem was first corrected in Windows
NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition
Service Pack 4.

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Keywords          : kbWinNT400sp4fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400 kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch kbAudDeveloper kbSBServSearch kbSBServ400 kbSBServ400a
Version           : WinNT:4.0,4.0a
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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