Updated Version of Dns.exe Fixes Several Problems

An updated version of Dns.exe is available to fix the following problems:

• A lookup for a non-existent A record takes about 30 seconds to time out: When the internal DNS server is queried, it goes to the root server. If the root server returns an RCODE of 0, the Microsoft DNS server does not respond to its client immediately. Some versions of BIND may return an RCODE of 0. This can cause a 30 second delay at the querying client.

• Problem resolving some MX records: If a DNS client does a recursive query to the Microsoft DNS server for an MX record and the authoritative DNS server for that MX record returns an SOA record instead (because the MX record doesn't exist), the Microsoft DNS server does not return that SOA record to the client. A BIND DNS server does return the SOA record to the DNS client even though it requested an MX record. Microsoft has modified its DNS service to be compatible with BIND.

• BIND incompatibility: When the Microsoft DNS service receives a query for a name that requires an authoritative lookup, and the DNS server handling the lookup is a BIND server, it may respond with a CNAME record, causing the name server (NS) record for the BIND server to be overwritten in cache. The NS record is used to specify the authoritative name server for a domain.

• When using the new WriteAuthorityNs reg key that was added in Windows NT 4.0 SP3 DNS, DNS queries will always return authority records=0 and additional=0 instead the actual count for this.

• If you delegate a zone (such as mydepartment.mycompany.com) to a DNS server that is not in the zone (such as yourserver.yourdepartment.company.com), when a client does a lookup on a host in the delegated zone, it will not succeed. If you ping the server that the zone was delegated to (yourserver.yourdepartment.company.com) once so that it is cached, lookups will start to succeed. The problem was caused by a problem following the glue record that was associated with the delegation, and it has been fixed.

• Access Violation in Dns.exe: Dr Watson may report an access violation on a secondary DNS server when it is receiving invalid records from the primary, and the data changes on the primary from the initial zone transfer.

Other updates and optimizations:

• Reduced traffic to root servers: This version eliminates the automatic root query on startup and in the timeout thread; instead, it queries the root only when it receives a query that needs to be sent to the root servers, and limits retrying the root servers to once every ten minutes.
• Better recursion response: This version supports direct forwarding of a response from the remote DNS, where possible.
• Eliminates a deadlock condition hit by a few customers. At least one person posting on the MS-DNS newsgroup reported hitting a deadlock. The symptom of this is that the server stops responding to all requests.
• Better use of SOA in authority section: This version still has an optimization to avoid this on local queries, but overall should be a more "friendly" partner for remote DNS servers when sending a NAME_ERROR or no-records response.
• Local network prioritization of queries: If there are multiple A records, this version of the server puts the one that "fits best" first; if none fits best, a straight round robin scheme is followed. This is off by default but can be turned on with the new LocalNetPriority registry flag:
  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Paramete
  Value Name: LocalNetPriority
  Data Type : REG_DWORD
  Data : 0 or 1 (0 is disabled)
  
  NOTE: This key does not exist by default.

For more information see the following article in the Microsoft Knowledge base:

• WildcardAllTypes registry flag: If on, this version of DNS will use wildcards on all types -- even where they make no sense; this was added for a specific customer scenario where it is used for a security check using reverse lookup.
• Cache pollution fix: There was a recently-publicized problem where a remote DNS returned bogus data, polluting the cache of DNS servers on the Internet. This was used to point some traffic that would normally go to InterNIC sites to another site. This release plugs that hole. All data received must be for names at or below the zone for which the NS is queried. For example, when you query the microsoft.com DNS server, you will accept any data for microsoft.com or ntdev.microsoft.com but will reject any data for someothersite.com.
• Non-port-53 operation: The purpose of this is to allow firewall of port 53 and still have the server go out and query the world. Anyone running a server on a firewall who is not interested in incoming traffic may be interested. You need to set the SendOnNonDnsPort registry key, to get non-53 sends. If you set this to a specific port > 1024, you actually run on that port, any < 1024 true value means you bind to any port.
  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Paramete
  Value Name: SendOnNonDnsPort
  Data Type : REG_DWORD
  Data : Desired Port#(53 is default)(port numbers are in decimal)
  
  NOTE: This key does not exist by default.
• No-forward of delegations: This is on by default. If you delegate foo.ntdev.microsoft.com to some server, that server is usually on your lan and you do not want to go through your forwarding server to reach it. To turn it off, set the ForwardDelegations registry key.
  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Paramete
  Value Name: ForwardDelegations
  Data Type : REG_DWORD
  Data : 0 or 1 (0 is disabled)
  
  NOTE: This key does not exist by default.

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, click the following article number to view the article in the Microsoft Knowledge Base:

Microsoft has confirmed that this is 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 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.

The hotfix mentioned above, may experience some problems as specified below:

• Local network prioritization of queries may cause Round-Robin load balancing to fail. If you experience this problem turn off the LocalNetPriority flag as mentioned above.
• High Speed Zone Transfers
  The default configuration does not attempt to include multiple records in each transaction. This may cause BIND 4.9.5 and newer DNS Servers to have slow zone transfers. If you experience this problem set the BindSecondaries flag to use faster zone transfers:
  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Paramete
  Value Name: BindSecondaries
  Data Type : REG_DWORD
  Data : 0 or 1 (0 = high speed; 1 = slower transfers)
  
  NOTE: This key does not exist by default. Transfers between Microsoft DNS Servers will always be done with using the faster, high compression method, regardless of how the BindSecondaries flag is set. After changing this registry key, you must stop and restart the DNS Server service.
  
  For more information see the following article in the Microsoft Knowledge base:
  ARTICLE-ID: 151416  (http://support.microsoft.com/kb/151416/EN-US/ )
  TITLE : Microsoft DNS Compatibility w/BIND Versions Earlier Than 4.9.4