DOCUMENT:Q192407 20-MAY-2002 [winnt] TITLE :Caching-Only DNS Server Incorrectly Reports "Name Error" PRODUCT :Microsoft Windows NT PROD/VER:WinNT:4.0 OPER/SYS: KEYWORDS: ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Workstation version 4.0 - Microsoft Windows NT Server version 4.0 ------------------------------------------------------------------------------- SYMPTOMS ======== A caching-only DNS server incorrectly returns a "Name Error" message when looking up a wildcard MX record. This occurs when another computer has recently looked up an "A" record with the same node name, and the "A" record is nonexistent. The record is held in cache on the caching-only server, and marked as Name Error. Future wildcard "MX" record lookups for the node name return Name Error until the cache is flushed on the caching- only DNS server. Some UNIX mail servers query for a type "A" host name before querying for an "MX" record and, therefore, may not be able to properly deliver mail when Name Error is returned. CAUSE ===== When the initial type "A" lookup is performed, the authoritative server replies with a "Name Error" message. The caching-only name server responds correctly by keeping this Name Error information in cache so that additional lookups do not require additional referrals from the authoritative DNS Server. When the wildcard "MX" request is received following the type "A" lookup, the caching server reads from cache and returns "Name Error" for the node. Only in the wildcard MX record case, where the "A" record would be nonexistent while the MX record would be resolvable, would an incorrect error be generated. RESOLUTION ========== A supported fix that corrects this problem is now available from Microsoft, but has not been fully regression tested and should be applied only to systems experiencing this specific problem. If you are not severely affected by this specific problem, Microsoft recommends that you wait for the next Windows NT service pack that contains this fix. To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web: http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS The English version of this fix should have the following file attributes or later: Date Time Size File Name Platform ------------------------------------------------------------- 08/22/98 12:48p 176,912 Dns.exe (x86) 08/22/98 01:04p 65,808 Nslookup.exe (x86) 08/22/98 12:47p 297,744 Dns.exe (Alpha) 08/22/98 01:02p 93,456 Nslookup.exe (Alpha) With the above fix, the authoritative name server responds to a query for a nonexistent hostname with error code 0. The caching-only server does not cache the name with error code 0, "No Error." Please note that Dns.exe must be replaced on the authoritative server. STATUS ====== Microsoft has confirmed this to be a problem in Windows NT version 4.0. ====================================================================== Keywords : Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 Version : WinNT:4.0 Hardware : ALPHA x86 Issue type : kbbug Solution Type : kbfix ============================================================================= 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. Copyright Microsoft Corporation 2002.