Microsoft TCP/IP Host Name Resolution OrderLast reviewed: December 18, 1997Article ID: Q172218 |
The information in this article applies to:
SUMMARYThis article discusses the different methods of host name to IP address resolutions used by Microsoft Windows clients. The sequence of methods is different than the sequence used to resolve NetBIOS names to IP addresses. MORE INFORMATION On a network using the TCP/IP protocol, it is necessary to convert names of resources to IP addresses to connect to these resources. Microsoft Windows clients will follow a sequence of methods in attempting to resolve a name to an address, stopping the search when it successfully matches a name to an IP address. There are two main sequences used in almost all cases: NetBIOS resolution and Host name resolution. Clients connecting to resources on Microsoft servers, typically through Windows File Manager or Network Neighborhood, most often use NetBIOS name resolution. For additional information, please see the following article in the Microsoft Knowledge Base:
ARTICLE-ID: Q119493 TITLE : NetBIOS over TCP/IP Name Resolution and WINSHost name resolution resolves the names of TCP/IP resources that do not connect through the NetBIOS interface. The most common example of this is a Web browser such as Microsoft Internet Explorer. Other examples include Internet applications such as Ping, FTP, and Telnet. Many modern database and mail applications that connect using Winsock, the Microsoft Windows implementation of TCP/IP sockets, also use host name resolution. When troubleshooting name resolution issues, it is important to narrow down whether the application is resolving a NetBIOS name or a host name. NOTE: In the context of this article, the term "client" does not necessarily refer to a workstation. A Windows NT server will take the role of client when it requires access to resources that require host name resolution. Host name resolution generally uses the following sequence:
For additional information, please see the following articles in the Microsoft Knowledge Base:
ARTICLE-ID: Q169141 TITLE : NetBIOS and hostname resolution for MS-Client and LM 2.2cWhen resolving names the client will skip methods for which it is not configured. For example, if there is no hosts file on the system, then it will skip step #2 above and try a query to a DNS server. If no DNS server IP addresses are entered in the client TCP/IP configuration, then the client will skip to the next step in the sequence after DNS. The method for changing host name resolution order differs among operating systems and versions. These are documented in the Resource Kits for the specific operating systems, as well as in the Microsoft Knowledge Base. For additional information, please see the following articles in the Microsoft Knowledge Base:
ARTICLE-ID: Q171567 TITLE : Windows NT 4.0 ServiceProvider Priority Values Not Applied ARTICLE-ID: Q139270 TITLE : How to Change Name Resolution Order on Windows 95 and Windows NT ARTICLE-ID: Q119372 TITLE : Setting the Name Resolution Search Order for TCP/IP-32 TroubleshootingProblem: Client is unable to resolve a host name. Troubleshooting steps: If a client cannot resolve a host name, then it is best to verify the Host name resolution sequence listed above that the client should be using. If the name does not exist in any of the resources that the client uses, then you must decide to which resource to add it. If the name exists in one of the resources, such as a DNS server or a Windows Internet Name Service (WINS) server and the client is not resolving the name correctly, focus your attention on troubleshooting that specific resource. Also, confirm that the client is trying to resolve a host name and not a NetBIOS name. Many applications have multiple methods that they can utilize to resolve names, this is especially true of mail and database applications. The application may be configured to connect to resources using NetBIOS. Depending on the client configuration the client may bypass host name resolution. From there it will be necessary to either change the connection type to TCP/IP sockets or to troubleshoot the problem as a NetBIOS issue. Problem: Client resolves a name very slowly, or fails to resolve a name and takes a long time to report a failure.Troubleshooting steps: Having DNS servers configured in a client's TCP/IP configuration, but the server is not available to the client usually causes this. Because the TCP/IP protocol assumes an unreliable network, a client will repeatedly attempt to connect to a DNS server before abandoning the attempted query. The client will then attempt to query a second DNS server if one is configured and take the same time to fail. Only then will the client step through to NetBIOS name resolution as described above. There are three ways to approach this issue.
File Name: Tcpipimp.doc Location : ftp://ftp.microsoft.com/bussys/winnt/winnt-docs/papers/ Title : "Microsoft Windows NT 3.5/3.51/4.0: TCP/IP Implementation Details TCP/IP Protocol Stack and Services, Version 2.0. " Keywords : ntnetserv NTSrvWkst nttcp win3x win95 kbnetwork Version : WinNT:3.5,3.51,4.0;Windows:3.1,3.11,95 Platform : WINDOWS Issue type : kbinfo Solution Type : Info_Provided |
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