Microsoft KB Archive/170059

= Microsoft DNS Resolvers' Behavior with Non-Microsoft Multihomed DNS =

Article ID: 170059

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Server 3.51
 * Microsoft Windows 95

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This article was previously published under Q170059



SYMPTOMS
This article discusses inconsistent behavior of Windows NT and Windows 95 Domain Name Service (DNS) resolvers with non-Microsoft multihomed DNS servers, when these name servers send their responses from addresses different from the one used to receive the query. This behavior is described below:

With Windows NT 4.0, if the DNS server responds to a query with a different source IP address than the one the request was sent to, Windows NT 4.0 accepts the response and continues.

With Windows NT 3.51 or Windows 95, if the DNS server responds to a query with a different source IP address than the one the request was sent to, Windows NT 3.51 or Windows 95 does NOT accept the response. If only one (primary) DNS server is listed, the client receives a "Bad IP Address" error message.

If a secondary DNS server is listed and responds to a query with a different source IP address than the one the request was sent to, Windows NT 3.51 or Windows 95 accepts the response, no matter what the source IP address of the response is, and continues.

NOTE: Windows NT 4.0 DNS servers respond to queries with the same source IP address that the request was sent to.



MORE INFORMATION
RFC1035 states:

7.3. Processing responses

- Some name servers send their responses from different addresses than the one used to receive the query. That is, a resolver cannot rely that a response will come from the same address which it sent the corresponding query to. This name server bug is typically encountered in UNIX systems.



STATUS
Microsoft has confirmed this to be a problem in Windows NT version 3.51 and Windows 95. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

Keywords: kbbug kbnetwork KB170059

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