WINS lookup integration
Updated: January 21, 2005
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
WINS lookup integration
Support for using Windows Internet Name Service (WINS) is provided to look up DNS names that cannot be resolved by querying the DNS domain namespace. To accomplish WINS lookup, two specific resource record types are used and can be enabled for any zones loaded by the DNS service:
The WINS resource record, which can be enabled to integrate WINS lookup into forward lookup zones
The WINS-R resource record, which can be enabled to integrate node adapter status request for reverse lookup zones
The WINS resource record
The WINS and DNS services are used to provide name resolution for the NetBIOS namespace and the DNS domain namespace, respectively. Although both DNS and WINS can provide a separate and useful name service to clients, WINS is mainly needed to provide support for older clients and programs that require support for NetBIOS naming.
However, the DNS service can work with WINS to provide combined name searches in both namespaces when resolving a DNS domain name not found in zone information. To provide this interoperability, a new record (the WINS record) was defined as part of the zone database file.
The WINS resource record is specific to computers running Windows NT 4.0 and earlier, Windows 2000, and Windows Server 2003 operating systems and can be attached only to the domain of origin for a zone. The presence of a WINS resource record can instruct the DNS service to use WINS to look up any forward queries for host names or names that are not found in the zone database. This functionality is particularly useful for name resolution required by clients that are not WINS-aware (for example, UNIX) for the names of computers not registered with DNS, such as Windows 95 or Windows 98 computers.
How WINS lookup works
The following is an example of a DNS client (host-b) querying its DNS server in an attempt to look up the address for another computer named host-a.example.microsoft.com..
In Step 1, the client queries its preferred DNS server. In Steps 2 through 8, the normal process of recursion proceeds as the preferred DNS server queries other DNS servers in succession on behalf of the client. This process concludes at Step 8, when the DNS server for the example.microsoft.com zone is located through the previous chain of referral answers. At this point in the process, the server contacted is a DNS server either running Windows NT Server 4.0, Windows 2000, or Windows Server 2003 .
When the DNS server for the example.microsoft.com zone receives the query for host-a, it looks in its configured zone to see if a matching address (A) resource record (RR) can be found. If no A record is found and the zone is enabled to use WINS lookup, the server does the following:
The DNS server separates the host part of the name (host-a) from the fully qualified domain name contained in the DNS query.
The host part of the name is the first label in the queried DNS domain name before a period is used in the name.
The server then sends a NetBIOS name request to the WINS server using the host name, host-a.
If the WINS server can resolve the name, it returns the IP address to the DNS server.
The DNS server then compiles an A resource record using the IP address resolved through the WINS server and returns this record to the original preferred DNS server that was queried by the requesting client, host-b.
The preferred DNS server then passes the query answer back to the requesting client.
How WINS reverse lookup works
There is also a WINS-R record or WINS reverse lookup entry that can be enabled and added to reverse lookup zones. However, because the WINS database is not indexed by IP address, the DNS service cannot send a reverse name lookup to WINS to get the name of a computer given its IP address.
Because WINS does not provide reverse lookup capability, the DNS service instead sends a node adapter status request directly to the IP address implied in the DNS reverse query. When the DNS server gets the NetBIOS name from the node status response, it appends the DNS domain name back onto the NetBIOS name provided in the node status response and forwards the result to the requesting client.
The WINS and WINS-R resource records are proprietary to the DNS Server service provided by Windows. You can prevent these resource records from being included in zone transfers to other DNS server implementations. For more information, see Using WINS lookup.