Microsoft KB Archive/182644

= DNR Now Sorts IP Addresses for a Multihomed Host Before Returning the List to Winsock Applications =

Article ID: 182644

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Server 4.0, Terminal Server Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows 95

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This article was previously published under Q182644





SYMPTOMS
When a Windows sockets client application connects to a server application on a multihomed server, it may not connect to the "nearest" or "best" IP address on that server.



CAUSE
When a Windows sockets application is used to connect to another computer, it normally calls gethostbyname to obtain the IP address of the target computer. This Winsock API invokes the Domain Name Resolver (DNR) component on the client computer to send a name query to a Domain Name Service (DNS) server. DNS returns a list of IP addresses to the DNR, which places the list into a structure and returns it to the application. Most applications then try to connect to the first IP address in the list.

An updated version of the DNR is now available. This version of the DNR sorts the list of IP addresses into the "best" order by examining the route table of the computer on which it is running. For instance, If any of the IP addresses in the list returned by the DNR are on a common subnet with the client, that IP address will be moved to the top of the list. This enhancement allows the client application to make the most direct connection possible to the server.



Windows NT 4.0
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:

152734 How to Obtain the Latest Windows NT 4.0 Service Pack

Windows 95
This issue is resolved by the following updated files for Windows 95 with the Winsock2 update for Windows 95 installed:   Mswsock.dll  version 4.10.1657  dated 4/8/98 4:57pm  71,168 bytes Rnr20.dll   version 4.10.1657  dated 4/8/98 4:57pm  43,520 bytes

NOTE: The Windows Sockets 2.0 (Winsock2) update for Windows 95 must be installed on Windows 95 prior to installing this update. For additional information, please see the following article in the Microsoft Knowledge Base:

182108 Availability of Windows Sockets 2.0 for Windows 95



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

Additional query words: multi-homed multi homed

Keywords: kbhotfixserver kbqfe kbbug kbfix kbqfe KB182644

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