Name Resolution

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Name Resolution

• 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

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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 DNS client to DNS server
• Iterative DNS server to DNS server
• Inverse Find a host name from a Known IP address

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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 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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Troubleshooting DNS

• Use nslookup from the command prompt

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Easy IP

• Dynamic Host Configuration Protocol

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Learning Objectives

• Describe the dynamic host configuration protocol
  (DHCP)
• Describe the dynamic IP leasing process
• Configure a client to use DHCP
• Install the DHCP server service
• Configure scopes within the DHCP server service

continued
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Learning Objectives

• Define and create scope options
• Authorize a DHCP server in Active Directory
• Configure DHCP for integration with DNS
• Manage, monitor, and troubleshoot DHCP

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Overview of DHCP

• Provides an easy way for network administrators
  to provide IP addressing information for network
  clients
• Reduces the work associated with moving clients
  between subnets
• DHCP server service can be used to create a pool
  of IP addresses known as scopes that can be
  dynamically assigned to clients
• Options can include default gateway address, or a
  DNS and a WINS server address

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DHCP Lease Process

• Discover
• Offer

• Request
• Acknowledgment

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Step 1 DHCPDiscover
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Step 2 DHCPOffer
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Step 3 DHCPRequest
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Step 3 DHCPRequest
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Step 4 DHCPAcknowledgment
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DHCP Renewal Process
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Configuring a Windows 2000 Server with the DHCP
Server Service

• Configure a static IP address, subnet mask, and
  default gateway on the server
• Install the DHCP server service
• Create scopes and, if needed
• Create and specify options on a server
• Authorize the DHCP server in Active Directory

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Client Configuration for DHCP

• Any client that supports a standard
  implementation of DHCP can obtain an IP address
  from a Windows 2000 DHCP server
• To configure Windows clients, specify that they
  obtain an IP address automatically by accessing
  the Internet Protocols (TCP/IP) properties found
  under Local Area Connections properties

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Client Configuration for DHCP
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Installing the DHCP Server Service

• Minimum requirements
• Windows 2000 server machine configured with a
  static IP address, subnet mask, and, on networks
  with multiple subnets or networks, a default
  gateway
• Range of addresses that can be used to create
  scopes (ranges of IP addresses configured for
  lease to clients via DHCP)
• Active Directory installed and configured to
  allow DHCP servers to be authorized in AD

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Installing the DHCP Server Service

• Many ways to install DHCP
• One of the easiest ways is to access Network and
  Dial-up connections via the Start menu or
  right-click on My Network Places and select
  Properties

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Installing DHCP
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Installing DHCP
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Installing DHCP

• Common problem on networks attempting to
  implement DHCP routers do not pass broadcasts
• Solutions
• Configure a router to pass DHCP traffic, using
  the command IP Helper-Address followed by the IP
  address of the DHCP server command
• Place second DHCP server on same segment as the
  client

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Router Blocking DHCPDiscover Packets
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Configuring a DHCP Server per Physical Segment
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Configuring Scopes
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Items in theNew Scope Wizard

• Name and Description
• IP Address range
• Subnet mask
• Add Exclusions
• Lease duration
• Configure DHCP Options

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Main Options Used with DHCP
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DHCP and Active Directory

• Create a DHCP object within Active Directory to
  validate DHCP servers
• Requirements
• All DHCP servers must run Windows 2000
• First DHCP server in your network must be
  installed as either a domain controller or member
  server

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Integrating DHCP and DNS

• You can configure DHCP to create Dynamic DNS
  entries for clients that do not support DDNS
• Helps with support of legacy, non-DDNS aware
  clients
• Windows clients can register their own A records
  but they still rely on the DHCP server to create
  reverse lookup records

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Integrating DHCP and DNS
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Troubleshooting DHCP

• Misconfigured scopes or options
• Use ipconfig/all command to verify client
  settings and information
• Change options within the DHCP snap-in
• A stopped DHCP server service
• Use the net start dhcpserver command

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Troubleshooting DHCP

• A scope that has run out of addresses
• Decrease length of lease for the scope
• Increase range of addresses in the scope
• Renumber entire scope with new, larger range of
  addresses
• Remove some clients from overcrowded network
  segment
• An improperly configured network
• Place a DHCP server on each subnet
• Implement DHCP forwarding on subnets without DHCP
  servers