Domain Name System

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Chapter 4

• Domain Name System

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Learning Objectives

• Provide an overview of the Domain Name System
  (DNS)
• Describe the features of DNS in Windows 2000
• Install the DNS server
• Configure a DNS server
• Create resource records manually
• Configure a client to use DNS
• Manage, monitor, and troubleshoot DNS

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DNS Overview

• Host names
• Simple names used as aliases for IP addresses
• DNS
• Hierarchical naming system used to resolve host
  name to IP address mapping
• Contains resource records
• Primary name resolution method in Windows 2000
• Host files and DNS perform the task of
  translating from names (host names) to IP
  addresses

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Host Files

• Text files that contain host name to IP address
  mapping
• Used to perform host name to IP address
  resolution
• Precursor to the DNS system
• Without host name resolution, users cannot access
  Internet or intranet resources via Fully
  Qualified Domain Names (FQDN)

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Ways to Perform Host Name to IP Address Resolution
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DNS Structure

• Root-level domain
• Represented by a period
• Usually not shown on FQDN
• Top-level domains
• Second-level domains
• Subdomains
• Individual hosts

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DNS Hierarchical Structure
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Top-level Domains

• Organizational domains created by designers of
  the Internet to simplify the naming and logical
  structure of the DNS namespace

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Second-level Domains and Subdomains

• Second-level domains
• Where companies register their names with a name
  registration company
• Gives the company authority to create subdomains
  to further divide the domain namespace

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DNS Zones

• Zone of authority
• Portion of the DNS namespace that an organization
  controls
• DNS zone
• Portion of the DNS namespace that can be
  administered as a single unit
• Each zone has a primary name server that holds
  the DNS zone file

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DNS Zones

• Primary name servers
• Hold a read/write copy of the zone file
• Secondary name servers
• DNS servers configured to hold a read-only copy
  of the primary name servers DNS zone file
• All networks should minimally have a primary and
  a secondary DNS name server, or two DNS servers
  configured to use Active Directory integrated
  zones

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DNS Servers

• Can be configured as caching-only servers
• Hold two types of DNS zones
• Forward lookup zones (host name to IP address
  mapping)
• Reverse lookup zones (IP address to host name
  mappings)

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DNS System

• Roles available to computers in DNS system
• DNS servers that answer client requests
• DNS resolvers clients that initiate requests
• Types of requests or queries
• Recursive
• Iterative
• Inverse

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Resource Records

• Used within the actual zone files to point to
  particular resources such as hosts, mail
  exchangers, and name servers

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Resource Records
continued
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Resource Records
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Windows 2000 DNS

• Supports incremental zone transfers
• Primary DNS servers send just the changes in the
  DNS database to a secondary server conserves
  network bandwidth
• Supports dynamic DNS as defined in RFC 2136
• Allows clients to register DNS information
  automatically with a DNS server
• Supports dynamic registration of clients that do
  not support DDNS through use of a service such as
  the Windows 2000 DHCP service

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Installing DNS Service

• Prerequisites
• Static IP address
• Subnet mask
• Default gateway
• Set the domain name suffix on the server

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Setting the Domain Name Suffix on the Server
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Installing DNS Service

• Use Optional Networking Components, accessible
  via the Advance menu in Network and Dial-up
  Connections

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Installing DNS Service
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Installing DNS Service

• Double-click Networking Services in the Windows
  Optional Networking Components Wizard and select
  the DNS service
• DNS management console is added to the
  Administrative Tools folder

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Installing DNS Service
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Configuring the DNS Server Service

• Configuring a root name server
• Configuring primary and secondary zones
• Configuring caching-only servers
• Configuring delegation for use with a subdomain
• Configuring the Windows DNS service to allow
  dynamic updates

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Configuring a Root Name Server

• Root name server
• Server that holds information about the overall
  Internet domain name servers
• Open the DNS management console, right-click
  Forward Lookup Zones, and select New Zone (See
  Figure 4-7)

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Configuring a Root Name Server
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Configuring a Root Name Server

• Choose a primary zone to configure a root zone
  server
• Choose a zone type
• Active Directory integrated
• Standard primary
• Standard secondary
• Name the zone

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Configuring a Root Name Server
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Configuring a Root Name Server
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Configuring a Root Name Server
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Configuring Primary and Secondary Zones

• DNS server
• Is configured as a primary name server for a
  particular zone or as a secondary or back-up,
  name server for a zone
• Can also be the primary server for one zone and
  the secondary server for another

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Configuring Primary and Secondary Zones
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Configuring Primary and Secondary Zones
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Configuring Primary and Secondary Zones
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Configuring Primary and Secondary Zones
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Configuring Primary and Secondary Zones

• Active Directory integrated zones
• Allow storage and replication of the DNS database
  within the AD database
• Ease the administrative tasks associated with
  manually setting up replication between primary
  and secondary name servers

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Configuring Caching-only Servers

• Caching-only server
• Is not authoritative for any particular DNS zone
  is not configured to hold a primary or secondary
  zone
• Forwards DNS requests and then caches the DNS
  resolutions

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Creating a Caching-only Server

• Load the DNS server service
• Configure forwarder addresses

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Configuring Caching-only Servers
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Implementing a Delegated Zone for DNS

• After creating subdomains, delegate authority for
  a zone via the New Delegation Wizard

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Configuring Zones for Dynamic Updates

• By default, standard zones on Windows 2000 DNS
  servers do not support dynamic registration

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Configuring Zones for Dynamic Updates

• Once configured to accept dynamic updates, all
  zones can allow Windows 2000 computers to create
  their own A records
• If your network uses DHCP, you can configure DHCP
  servers to register PTR records for Windows 2000
  clients and A and PTR records for non-Windows
  2000 clients

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Configuring Zones for Dynamic Updates
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Creating Resource Records Manually
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DNS Client Configuration

• For clients with static IP addresses
• Manually configure a Preferred DNS server and an
  Alternate DNS server in TCP/IP properties DNS
  configuration tab for Windows 95/98 clients
• For DHCP clients
• Configure DNS options for the scope that the
  client will obtain an IP address from

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Basic Manual DNS Configuration for Windows 2000
Clients
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Advanced Manual DNS Configuration
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Managing, Monitoring, and Troubleshooting DNS

• Setting TTL properties
• Zone transfer settings
• Monitoring and testing tools

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Setting TTL Properties

• Cache entries are maintained for a length of time
  determined by the time-to-live setting of the
  zones on a server
• By default, TTL is one day
• Refresh interval
• Retry interval

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Setting TTL Properties
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Zone Transfer Settings

• Configure additional zone transfer settings to
  ensure optimal exchange of database information

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Monitoring and Testing Tools

• Test utilities for testing and logging DNS server
  activity
• Simple graphical tool
• nslookup

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Using the Simple Graphical Tool

• Perform a simple query that attempts a forward
  lookup query
• Perform a recursive query
• Perform the test immediately with Test Now
  button, or have tests occur automatically at a
  preset interval

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Using the Simple Graphical Tool

• Use DNS log in EventViewer for more detailed
  logging and information

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Using the nslookup Utility

• Allows an administrator to query DNS servers for
  information about resource records within the DNS
  database
• Can perform a single lookup in non-interactive
  mode
• Can perform a series of lookups in interactive
  mode

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Chapter Summary

• Domain name system overview
• Installing DNS service
• Configuring the DNS server service
• Creating resource records manually
• DNS client configuration
• Managing, monitoring, and troubleshooting DNS