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Chapter 3: Configuring the DNS Service
About This Chapter
Domain Name System (DNS) is a distributed database that is used in Transmission Control Protocol/Internet Protocol (TCP/IP) networks to translate computer names to Internet Protocol (IP) addresses. This chapter helps you understand DNS and name resolution. It also presents the skills and knowledge necessary to install and configure the DNS Service.
Before You Begin
To complete this chapter
- You must have installed Windows 2000 Server on a computer that meets or exceeds the minimum hardware requirements listed in "Getting Started." The computer should be installed as a stand-alone computer in a workgroup and TCP/IP should be the only installed protocol.
Lesson 1: Understanding DNS
DNS is most commonly associated with the Internet. However, private networks use DNS extensively to resolve computer names and to locate computers within their local networks and the Internet. DNS provides the following benefits:
- DNS names are user-friendly, which means that they are easier to remember than IP addresses.
- DNS names remain more constant than IP addresses. An IP address for a server can change, but the server name remains the same.
- DNS allows users to connect to local servers by using the same naming convention as the Internet.
For more information on DNS, see RFC 1034 and RFC 1035. To read these RFCs (Requests for Comment), use your Web browser to search for "RFC 1034" and "RFC 1035" on the Internet.
After this lesson, you will be able to
- Explain the function of DNS and its components.
Estimated lesson time: 15 minutes
Domain Name Space
The domain name space is the naming scheme that provides the hierarchical structure for the DNS database. Each node represents a partition of the DNS database. These nodes are referred to as domains.
The DNS database is indexed by name; therefore, each domain must have a name. As you add domains to the hierarchy, the name of the parent domain is appended to its child domain (called a subdomain). Consequently, a domain's name identifies its position in the hierarchy. For example, in Figure 3.1, the sales.microsoft.com domain name identifies the sales domain as a subdomain of the microsoft.com domain and microsoft as a subdomain of the com domain.
The hierarchical structure of the domain name space consists of a root domain, top-level domains, second-level domains, any subdomains, and host names.
The term domain, in the context of DNS, is not related to domain as used in the Microsoft Windows 2000 directory services. A Windows 2000 domain is a grouping of computers and devices that are administered as a unit.
Figure 3.1 Hierarchical structure of a domain name space
The root domain is at the top of the hierarchy and is represented as a period (.). The Internet root domain is managed by several organizations, including Network Solutions, Inc.
Top-level domains are two- or three-character name codes. Top-level domains are organized by organization type or geographic location. Table 3.1 provides some examples of top-level domain names.
Table 3.1 Top-Level Domains
|au||Country code of Australia|
Top-level domains can contain second-level domains and host names.
Organizations, such as Network Solutions, Inc., assign and register second-level domains to individuals and organizations for the Internet. A second-level name has two name parts: a top-level name and a unique second-level name. Table 3.2 provides some examples of second-level domains.
Table 3.2 Second-Level Domain Examples
|ed.gov||United States Department of Education|
|w3.org||World Wide Web Consortium|
|pm.gov.au||Prime Minister of Australia|
Organizations can create additional names that extend their DNS tree to represent departments, divisions, or other geographic locations. Subdomains have three name parts: a top-level name, a unique second-level name, and a unique name representing the department or location—for example, sales.microsoft.com.
Host names refer to specific computers on the Internet or a private network. For example, in Figure 3.1, Computer1 is a host name. A host name is the leftmost portion of a fully qualified domain name (FQDN), which describes the exact position of a host within the domain hierarchy. Computer1.sales.microsoft.com. (including the end period, which represents the root domain) is an FQDN (see Figure 3.1).
DNS uses a host's FQDN to resolve a name to an IP address. The host name does not have to be the same as the computer name. By default, TCP/IP setup uses the computer name for the host name, replacing illegal characters, such as the underscore (_), with a hyphen (-).
For the accepted domain naming conventions, see RFC 1035.
Domain Naming Guidelines
When you create a domain name space, consider the following domain guidelines and standard naming conventions:
- Limit the number of domain levels. Typically, DNS host entries should be three or four levels down the DNS hierarchy and no more than five levels down the hierarchy. The numbers of levels increase the administrative tasks.
- Use unique names. Each subdomain must have a unique name within its parent domain to ensure that the name is unique throughout the DNS name space.
- Use simple names. Simple and precise domain names are easier for users to remember and enable users to search intuitively and locate Web sites or other computers on the Internet or an intranet.
- Avoid lengthy domain names. Domain names can be up to 63 characters, including the periods. The total length of an FQDN cannot exceed 255 characters. Case-sensitive naming is not supported.
- Use standard DNS characters and Unicode characters.
- Windows 2000 supports the following standard DNS characters: A-Z, a-z, 0-9, and the hyphen (-), as defined in RFC 1035.
- The DNS Service also supports the Unicode character set. The Unicode character set includes additional characters not found in the American Standard Code for Information Interchange (ASCII) character set, that are required for languages such as French, German, and Spanish.
Use Unicode characters only if all servers running the DNS Service in your environment support Unicode. For more information on the Unicode character set, see RFC 2044.
A zone represents a discrete portion of the domain name space. Zones provide a way to partition the domain name space into manageable sections.
- Multiple zones in a domain name space are used to distribute administrative tasks to different groups. For example, Figure 3.2 depicts the microsoft.com domain name space divided into two zones. The two zones allow one administrator to manage the microsoft and sales domains and another administrator to manage the development domain.
- A zone must encompass a contiguous domain name space. For example in Figure 3.2, you could not create a zone that consists of only the sales.microsoft.com and development.microsoft.com domains, because these two domains are not contiguous.
Figure 3.2 Domain name space divided into zones
The name-to-IP address mappings for a zone are stored in the zone database file. Each zone is anchored to a specific domain, referred to as the zone's root domain. The zone database file does not necessarily contain information for all subdomains of the zone's root domain, only those subdomains within the zone.
In Figure 3.2, the root domain for Zone1 is microsoft.com, and its zone file contains the name-to-IP-address mappings for the microsoft and sales domains. The root domain for Zone2 is development, and its zone file contains the name-to-IP-address mappings for the development domain only. The zone file for Zone1 does not contain the name-to-IP-address mappings for the development domain, although development is a subdomain of the microsoft domain....