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

ID: Q182644

The information in this article applies to:

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.


RESOLUTION

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:
Q152734 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:
Q182108 Availability of Windows Sockets 2.0 for Windows 95


STATUS

Windows NT 4.0

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 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.

Additional query words: multi-homed multi homed 


Keywords          : NT4SP4Fix kbbug4.00 kbfix4.00.sp4 NTSrvWkst 
Version           : WINDOWS:95; winnt:4.0
Platform          : WINDOWS winnt 
Issue type        : kbbug

Last Reviewed: July 1, 1999