KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q253253: Proxy: WSP Clients Cannot Reach Remote Segments of the LAN

Article: Q253253
Product(s): Microsoft Windows NT
Version(s): winnt:1.0,2.0,4.0
Operating System(s): 
Keyword(s): kbenv
Last Modified: 08-AUG-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows NT Server version 4.0 
- Microsoft Proxy Server versions 1.0, 2.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

Local area network (LAN) clients that are using the Winsock Proxy (WSP) client
may be unable to reach certain segments of the the LAN if those segments are
separated by a router and on a logically different TCP/IP Network ID.

For example, this behavior may occur if one office is connected to another office
(possibly across town) with a router and one or both offices may have its own
independent Proxy servers for Internet connectivity. Or, a second office may
have been added to the network after the Proxy server was initially set up.

Even though the router provides IP routing, clients that are configured to access
the Internet by using a Winsock proxy through the Proxy server may not be able
to connect to computers on the LAN across their router.

CAUSE
=====

This behavior can occur if the local address table (LAT) on the Proxy server
does not include the remote LAN's IP address range or Network ID.

The WSP client program consults the local copy of the LAT to make decisions about
routing the IP packets. If the destination is in the LAT, it lets them pass
through. If the destination is not in the LAT, the WSP client intercepts it,
repackages it in the WSP protocol, and forwards it to the Proxy server to be
transmitted to the internet.

Note that only Winsock Proxy requests consult the (LAT) to determine which route
to take.

RESOLUTION
==========

To resolve this issue, add the network address ranges that are in use on all the
LANs you need to gain access to without going through the Proxy server. (By
definition, this information is what constitutes the LAT.)

You can add to or change the LAT on the Proxy server by clicking Start, pointing
to Programs, clicking Proxy Administration, clicking Winsock or Web Proxy
Service, clicking the Service tab, and then clicking Local Address Table.

Clients receive a copy of the LAT at the next restart, or you can force a new
copy by clicking Update Now in the WSP Client tool in Control Panel on the
client computers.

Additional query words:

======================================================================
Keywords          : kbenv 
Technology        : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbAudDeveloper kbProxyServ100 kbProxyServSearch kbProxyServ200
Version           : winnt:1.0,2.0,4.0
Issue type        : kbprb

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.