DOCUMENT:Q247419  06-AUG-2002  [exchange]
TITLE   :XCON: TCP/IP Control Block Shortage Event ID 9156
PRODUCT :Microsoft Exchange
PROD/VER:winnt:5.5 SP3
OPER/SYS:
KEYWORDS:exc55sp3 kbExchange550preSP4fix kbExchange550sp4Fix

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The information in this article applies to:

 - Microsoft Exchange Server, version 5.5 SP3 
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SYMPTOMS
========

After you apply Service Pack 3 for Exchange Server version 5.5, the following
error message may be logged in the Windows NT Event Viewer application event
log:

   Event ID: 9156
   Source: MSExchangeMTA
   Type: Warning
   Category: Resource
   Description:
   A resource limit has been reached while attempting to open an association.
   There is no free control blocks available for network type 1.
   The configured count is 40. [BASE IL MAIN BASE 1 282] (10)

After this error message is logged, the message transfer agent (MTA) may stop
processing messages and you may need to restart the service before mail flows
again.

CAUSE
=====

The MTA leaks control blocks. Under stress or slow connection conditions this
issue becomes apparent.

RESOLUTION
==========

To resolve this problem, obtain the latest service pack for Exchange Server 5.5.
For additional information, click the following article number to view the
article in the Microsoft Knowledge Base:

   Q191014 XGEN: How to Obtain the latest Exchange Server 5.5 Service Pack


WORKAROUND
==========

You can use the Evtscan utility from the BackOffice Resource Kit to stop and
start the MTA as soon as you detect a 9156 event in the application event log.

STATUS
======

Microsoft has confirmed that this is a problem in Microsoft Exchange Server
version 5.5 Service Pack 3. This problem was first corrected in Exchange Server
5.5 Service Pack 4.

Additional query words: bridgehead slow link bork

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Keywords          : exc55sp3 kbExchange550preSP4fix kbExchange550sp4Fix 
Technology        : kbExchangeSearch kbZNotKeyword2 kbExchange550SP3
Version           : winnt:5.5 SP3
Issue type        : kbbug
Solution Type     : kbfix

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