【正文】 is used on TCP/IP works, such as the Inter and most corporate works, to locate puters and services by using userfriendly names. When a user enters the DNS name of a puter in an application, DNS can look up the name and provide other information that is associated with the puter, such as its IP address or services that it provides for the work. This process is called name resolution. Name systems, such as DNS, make it easier to use work resources by providing users with a way to refer to a puter or service by a name that is easy to remember. DNS looks up that name and provides the numeric address that operating systems and applications require to identify the puter on a work. For example, users enter instead of the numeric IP address of the server to identify a Microsoft Web server on the Inter. The name is resolved when the DNS client software on the user39。s puter is configured to use. If the DNS server has been configured to respond authoritatively with the address of the requested host, it replies to the request directly. Otherwise, the DNS server passes the request on to another server that can provide the address or a referral to another DNS server that can help provide the address. This is where the name hierarchy es into play: If a DNS server does not know which server is configured with the address, it can request the server that is responsible for maintaining addresses of servers at each level in the hierarchy until it locates the authoritative server. For example, if the DNS server does not know which server is responsible for the server named , the DNS server can ask the server that is responsible for supplying the names of DNS servers in the . domain to provide the address of the server that is responsible for providing the addresses of DNS servers in the domain. The original DNS server can then query that server for the address of the puter named . DNS requires little ongoing maintenance for small businesses, which typically have one to four DNS servers. (Mediumsize anizations usually have 4 to 14 DNS servers.) DNS problems, however, can affect server availability for your entire work. Most DNS problems occur because DNS settings are configured incorrectly or obsolete records remain on the DNS servers. By following the procedures in this guide, you can avoid such problems when you deploy DNS in a simple work that is based on the Windows Server174。 Domain Services (AD DS) domain. The guide then addresses some advanced issues that mediumsize anizations may have to consider. Finally, it includes some basic DNS troubleshooting steps that you can take if you suspect that your environment has problems with DNS. In this guide 6 ?? Planning DNS ?? Installing and Configuring AD DS and DNS ?? Configuring Client Settings ?? Advanced DNS Configuration ?? Troubleshooting DNS Planning DNS Domain Name System (DNS) is the primary method for name resolution in Windows Server174。 Windows174。s name, such as or . Most small anizations work with their Inter service provider (ISP) to register their domain name, although you can also register your domain name directly with a registrar that is listed at InterNIC ( Registering an Inter domain name reserves the name for the exclusive use of the anization and configures DNS servers on the Inter to provide the appropriate IP address when those servers are queried for that name. That is, it creates the equivalent of a telephone directory entry for the Inter domain name. But instead of providing a telephone number for the name, it provides the IP address that a puter requires to access the puters in the registered domain. The DNS namespace is not limited to only the publicly registered Inter domain names. Organizations that have works with their own DNS servers can create domains for their internal use. As the next section explains, these internal DNS namespaces can be—but are not required to be—subdomains of a public Inter domain name. Designing a DNS namespace You can design an external namespace that is visible to Inter users and puters. You can also design an internal namespace that is visible only to users and puters that are in your internal work. Organizations that require an Inter presence and an internal namespace must deploy both an internal and an external DNS namespace and manage each namespace separately. In this case, we remend that you make your internal domain a subdomain of your external domain. For example, an anization that has an external domain name of might use the internal domain name . Using an internal domain that is a subdomain of an external domain has the following advantages: ?? Requires you to register only one name with an Inter name authority even if you later decide to make part of your internal namespace publicly accessible. ?? Ensures that all of your internal domain names are globally unique. ?? Simplifies administration by enabling you to administer internal and external domains separately. 9 ?? Allows you to use a firewall between the internal and external domains to secure your DNS deployment. If you want to deploy an AD DS domain for each division in your anization, you can use your internal domain as a parent for additional child domains that you create to manage those divisions. Child domain names are immediately subordinate to the domain name of the parent. For example, a child domain for a manufacturing division that you add to the namespace might have the domain name . Creating an Inter DNS domain name An Inter DNS domain name has a TLD name, such as ., ., or .edu, and a unique subdomain name that the domain owner chooses. For example, a pany named Contoso Corporation would probably choose as its Inter domain name. Before you register an Inter DNS domain, conduct a preliminary search of the Inter to confirm that the DNS domain name that