Using WINS lookup

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Using WINS lookup

The DNS Server service provides the ability to use Windows Internet Name Service (WINS) servers to look up names not found in the DNS domain namespace by checking the NetBIOS namespace managed by WINS.

To use WINS lookup integration, two special resource record (RR) types--the WINS and WINS-R resource records--are enabled and added to a zone. When the WINS RR is used, DNS queries that fail to find a matched host (A) RR in the zone are forwarded to WINS servers configured in the WINS RR. For reverse lookup zones, the WINS-R RR can be enabled and used to provide a similar benefit for further resolving a reverse query not answerable in the reverse in-addr.arpa domain.

A good example of when to use WINS lookup is when you are using a mixed-mode client environment consisting of UNIX clients that use only DNS name resolution and earlier-version Microsoft clients that require NetBIOS naming. In these environments, WINS lookup provides a method for permitting UNIX DNS clients to locate your WINS clients by extending DNS host name resolution into the WINS-managed NetBIOS namespace.

The WINS lookup integration feature is only supported by Windows DNS servers. If you use a mixture of Windows and other DNS servers to host a zone, you should enable the Do not replicate this record check box option for any primary zones when using the WINS lookup record. This prevents the WINS lookup record from being included in zone transfers to other DNS servers that do not support or recognize this record. If you do not enable the WINS lookup record to be used only on the local server, it can cause data errors or failed zone transfers at servers running other DNS server implementations that replicate the zone.

The following sections discuss WINS lookup interoperability considerations and explain the following:

• How the caching Time-To-Live (TTL) and lookup time-out values are configured for use with the WINS and WINS-R records.

• The format of the WINS and WINS-R resource records as they are used in zone files created by the DNS Server service.

WINS lookup interoperability

Typically, WINS lookup provides the best and most predictable results if only Windows DNS servers are used, and is only available directly for use at Windows DNS servers. There are ways, however, that you use and benefit from WINS lookup as an interoperable solution when other DNS servers are deployed.

For example, consider adding a Windows DNS server that hosts a new WINS lookup-enabled zone. When creating and naming the zone, use a subdomain added to your existing DNS namespace that is used just for WINS-specific referrals added to your DNS domain namespace.

For instance, in example.microsoft.com, call the zone wins.example.microsoft.com when you create it. You can then use this new WINS referral zone as the root zone for any of your WINS-aware computers with names that are not found in your other traditional DNS zones.

In order to use the WINS referral zone, you need to specify its domain name (wins.example.microsoft.com) in a DNS suffix search list for your clients. The suffix list is configurable as part of the TCP/IP properties for a client connection and can be updated either manually, using DHCP, or using Group Policy. As long as the name of the WINS referral zone is included in the domain suffix list, any DNS names not resolved in traditional zones can be resolved using the WINS referral subdomain.

Under normal conditions, this should result in recursion from your other DNS servers to the Windows DNS servers that host the WINS-enabled zone. If the queried host names match NetBIOS computer names found in the WINS database, the names are resolved to the IP addresses mapped in WINS data there.

In our example the WINS-enabled zone is only used for WINS lookup, therefore no additional resource records need to be added to it. In general, WINS records could be added to any forward lookup zone.

By using a specific subdomain just for WINS lookup and specifying a static DNS suffix list to be used in resolving and searching for names, you can prevent unusual situations in which DNS queries for different FQDNs resolve to the same WINS client name and IP address. This might easily occur if you add and configure many zones at each level of your namespace and enable each of them to use WINS lookup integration.

For example, suppose you have two zones both configured to use WINS lookup. The zones are rooted and originate at the following DNS domain names:

example1.microsoft.com.

example2.microsoft.com.

With this configuration, a WINS client named HOST-A could be unintentionally resolved using either of the following FQDNs:

host-a.example1.microsoft.com.

host-a.example2.microsoft.com.

WINS resource record

Description:  WINS forward lookup resource record. Used in a zone to provide further resolution of DNS queries for names not found in the zone by using a name query to WINS servers configured and listed with this record. If used, the WINS record only applies for the topmost level within a zone and not for subdomains used in the zone. The various fields that are used with the WINS RR include the following: owner  Indicates the owner domain for this record, should always be set to "@" to indicate that the current domain is the same as the zone origin. class  Indicates the class for this record, should always be set to "IN" as the Internet class is the only supported class for DNS servers running Windows Server 2003. LOCAL  When used, indicates that the WINS RR is to used only locally at the DNS server and is not to be included during zone replication with other DNS servers. This field corresponds to whether the Do not replicate this record check box was selected when configuring WINS lookup at the DNS console. If this check box was cleared, this field will not be included when the record is written to the zone. lookup_timeout  The lookup time-out value to be applied for this record. cache_timeout  The cache time-out value to be applied for this record. wins_ip_addresses  Used to specify one or more IP addresses of WINS servers. At least one IP address of a valid WINS server is required.

Syntax:  owner  class  WINS  [LOCAL]  [Llookup_timeout]  [Ccache_timeout]  wins_ip_addresses

Example: @ IN WINS 10.0.0.1 @ IN WINS LOCAL L1 C10 10.10.10.1 10.10.10.2 10.10.10.3

Note

• In the provided example WINS records, the zone root is assumed to be the current origin.

WINS-R resource record

Description: WINS reverse lookup resource record. Used in a reverse lookup zone to provide further resolution for reverse queries not found in the zone by using a NetBIOS adapter node status query sent to the queried IP addresses. When this record is used, you need to specify the parent domain to be appended to a NetBIOS computer name when a successful reverse lookup occurs. Other fields used in the WINS-R record have similar description and purpose as described previously for their use in the WINS forward lookup record.

Syntax:  owner  class  WINS  [LOCAL]  [Llookup_timeout]  [Ccache_timeout]  Domain_to_append_to_returned_NetBIOS_names

Example:  @ IN WINS-R LOCAL L1 C10 example.microsoft.com. @ IN WINS-R wins.example.microsoft.com.

Note

• In the provided example WINS-R records, the zone root is assumed to be the current origin.

Advanced parameters for WINS lookups

Two following advanced timing parameters are used with the WINS and WINS-R records:

• The Cache timeout value, which indicates to a DNS server how long it should cache any of the information returned in a WINS lookup. By default, this value is set to 15 minutes.

• The Lookup timeout value, which specifies how long to wait before timing out and expiring a WINS lookup performed by the DNS Server service. By default, this value is set to 2 seconds.

These parameters are configured using the Advanced button in the zone properties dialog box when you configure the zone. This button appears on either the WINS or WINS-R tab, depending on whether the zone you are configuring is being used for forward lookup or reverse lookup.

If you are using either the WINS or WINS-R resource record, be aware that the minimum Time-To-Live (TTL) set in the SOA record for the zone is not the default TTL used with these records. Instead, when either an IP address or a host name gets resolved with WINS lookup, the information is cached on the DNS server for the amount of time configured for the WINS cache time-out value. If this address is then ever forwarded to another DNS server, the WINS cache time-out value TTL is what is sent. If your WINS data rarely changes, you can increase the default TTL of 15 minutes.

Notes

• If you have a zone configured for WINS lookup, then all DNS servers that are authoritative for that zone need to be capable of WINS lookup or you will have intermittent behavior.

• Because you can select that the WINS and WINS-R RRs not be replicated to other DNS servers, you can selectively enable and configure WINS lookup at each of your secondary servers for zones where this feature is used. This is not a standard practice for other types of resource records which are only to be configured at the primary server for the zone.

For more information, see Enable DNS to use WINS resolution.