IMPLEMENTING NAME RESOLUTION USING DNS Chapter 3 IMPLEMENTING NAME RESOLUTION USING DNS Briefly describe the topics covered in the chapter. Refer to the objectives list at the beginning of Chapter 3.

WHAT IS NAME RESOLUTION? Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS WHAT IS NAME RESOLUTION? Name resolution is the process that translates computer names that are easy for users to understand to numerical Internet Protocol (IP) addresses, which are difficult for users to remember but necessary for TCP/IP communications. Explain that DNS and WINS are two services that provide name resolution. This chapter discusses DNS, which translates fully qualified domain names (FQDNs) into IP addresses and is required for Microsoft Windows 2000 and Microsoft Windows Server 2003 networks. Windows Internet Naming System (WINS) is not covered in this chapter because it is only necessary with pre–Windows 2000 clients and is used to translate computer names or host names to IP addresses.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS OVERVIEW OF DNS Benefits of DNS Scalability Constancy Ease of use DNS overview Domain Name System (DNS) DNS zones Types of DNS servers DNS resource records DNS resolvers Provide students with a brief history of name resolution emphasizing the efficiency of DNS. Mention that dynamic updates did not exist until Windows 2000 and that DNS is a major step toward providing the scalability necessary for the growth of the Internet.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS DOMAIN NAMESPACE Explain the hierarchical structure of DNS or the Internet namespace. Mention that the root domain is represented by a period (.), which is not used when writing a FQDN or typing a URL. Illustrate an example on the white board, such as training.microsoft.com, and point out on the graphic what each layer represents in the sample domain name.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS INSTALLING DNS Explain the options for installing DNS: The Manage Your Server page Add Or Remove Programs in Control Panel Discuss why it is necessary for DNS servers to use static IP addresses. Also mention that DNS is a required service if the network is running Active Directory directory service.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS DNS ZONES Zones are classified based on where the DNS database is stored and whether the database is writable or read-only. The next two slides explain the zone types in more detail.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS STANDARD ZONES S t a n d r Z o e T y p D s c i Standard primary Contains a read/write copy of the database Standard secondary Contains a read-only copy of in- addr.arpa Used for reverse lookups Stub Contains the resource records that identify the authoritative DNS server for the domain

ACTIVE DIRECTORY–INTEGRATED ZONES Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS ACTIVE DIRECTORY–INTEGRATED ZONES Zone types Forward lookup Reverse lookup Benefits Fault tolerance Security Multimaster Efficient replication Secondary zones Explain that an Active Directory–integrated zone stores the DNS database in Active Directory and is replicated as a part of normal Active Directory replication. For this reason, all DNS servers must be located on domain controllers. Explain forward and reverse lookup zones, and emphasize that a reverse lookup zone is similar to an in-addr.arpa zone. Also point out that unlike standard zones, DNS servers do not have a hierarchy because Active Directory–integrated DNS servers have read/write copies of the DNS database.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS ROOT HINTS To resolve a query for a name over which it does not have authority, the DNS server must have the addresses of additional DNS servers so that it can forward requests to those servers. The list of additional servers is referred to as root hints. Explain that by default DNS servers use the root hints that are stored in the Cache.dns file. This slide illustrates the properties page in the DNS console that allows you to configure or manage root hints.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS DNS SERVER TYPES D N S e r v T y p s c i t o n Primary name server One or more primary zones Secondary name server One or more secondary zones Master name server Responsible for sending updates Caching-only name server Does not host any zones Explain the role of each server type and how one server can perform more than one role. For example, a server can be a primary server, a secondary server, or both.

DNS RESOURCE RECORD TYPES Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS DNS RESOURCE RECORD TYPES Start of authority (SOA) Name server (NS) Host address (A) Pointer (PTR) Canonical name (CNAME) Mail exchanger (MX) Service locator (SRV) Other record types DNS resource record types can indicate a single host, such as an A record, or they can indicate a network service, such as an SRV record. Demonstrate how to view the DNS records. Briefly discuss the purpose of each record type. When you discuss the additional record types, be sure to mention delegation records, glue records, and wildcard resource records.

USING ITERATIVE QUERIES IN THE DNS QUERY PROCESS Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS USING ITERATIVE QUERIES IN THE DNS QUERY PROCESS Explain iterative queries and emphasize that the client is ultimately responsible for making sure the name is resolved.

USING RECURSIVE QUERIES IN THE DNS QUERY PROCESS Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS USING RECURSIVE QUERIES IN THE DNS QUERY PROCESS Using recursive queries, the DNS server takes responsibility for returning a definitive answer. Explain to students that this is the preferred method for most queries because it centralizes the query process to the DNS server rather than having it spread among several hosts. Also explain to students that recursion can be disabled if clients need to resolve names located on a local intranet.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS QUERY RESPONSES Positive answer Authoritative answer Referral answer Negative answer Explain to students that, so far, we have only looked at and considered situations in which the DNS query was successful. Point out that DNS queries are not always successful. Briefly discuss each of the query responses.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS NAME SERVER CACHING Improves query response time Reduces network traffic When clients place queries, the DNS server will check its resolver cache for an entry that matches the client’s request. If there is a match, the DNS server can respond with the cached entry rather than contacting other DNS servers. This process can substantially speed up the recursive query process.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS DELEGATING ZONES This slide illustrates zone delegation for the sales.contoso.com domain from the parent domain contoso.com. A DNS zone initially creates a database for a single domain and is authoritative for the single domain name. If subdomains are added, you might decide, for administrative purposes, to delegate authority for the subdomain by creating an additional DNS zone on another DNS server. You might also use additional zones to create fault tolerance or improve DNS performance.

UNDERSTANDING ZONE TRANSFERS Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS UNDERSTANDING ZONE TRANSFERS Explain the zone transfer process by referring to the slide. Point out that the secondary server always initiates zone transfers. Explain how DNS Notify allows the primary server to notify the secondary server about updates (the secondary does not have these updates). Point out that Active Directory–integrated zones handle replication through Active Directory replication, not through the DNS notify process.

CONTROLLING WHICH SERVERS ARE NOTIFIED OF UPDATES Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS CONTROLLING WHICH SERVERS ARE NOTIFIED OF UPDATES DNS Notify provides a method for the primary server to notify the secondary servers when the database has changed. For security purposes, Windows Server 2003 allows an administrator to control which secondary servers are notified.

UNDERSTANDING FORWARDING Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS UNDERSTANDING FORWARDING Standard forwarding Conditional forwarding Explain standard and conditional forwarding. Emphasize how the use of forwarders can make the network more efficient and more secure.

Chapter 3: IMPLEMENTING NAME RESOLUTION USING DNS SUMMARY What is DNS? DNS zone types Root hints DNS server types DNS record types DNS query process Delegating zones Zone transfer Forwarding