Name Resolution
Domain Name System
Learning Objectives
4
 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
DNS Overview
4
 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
Host Files
4
 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)
4
Ways to Perform Host Name
to IP Address Resolution
DNS Structure
4
 Root-level domain


Represented by a period
Usually not shown on FQDN
 Top-level domains
 Second-level domains
 Subdomains
 Individual hosts
DNS Hierarchical Structure
4
Top-level Domains
4
 Organizational domains created by designers
of the Internet to simplify the naming and
logical structure of the DNS namespace
Second-level Domains and
Subdomains
4
 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
DNS Zones
4
 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
DNS Zones
4
 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 server’s DNS zone file
 All networks should minimally have a
primary and a secondary DNS name server
DNS Servers
4
 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)
DNS System
4
 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
Resource Records
4
 Used within the actual zone files to point to
particular resources such as hosts, mail
exchangers, and name servers
Resource Records
4
continued
Resource Records
4
Windows 2000 DNS
4
 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
Installing DNS Service
4
 Prerequisites




Static IP address
Subnet mask
Default gateway
Set the domain name suffix on the server
4
Setting the Domain Name
Suffix on the Server
Installing DNS Service
4
 Use Optional Networking Components,
accessible via the Advance menu in Network
and Dial-up Connections
Installing DNS Service
4
Installing DNS Service
4
 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
Installing DNS Service
4
4
Configuring Zones for
Dynamic Updates
 By default, standard
zones on Windows
2000 DNS servers do
not support dynamic
registration
4
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
4
Configuring Zones for
Dynamic Updates
4
Creating Resource Records
Manually
DNS Client Configuration
4
 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
4
Basic Manual DNS Configuration
for Windows 2000 Clients
Troubleshooting DNS
4
 Use nslookup from the command prompt
Easy IP
Dynamic Host Configuration
Protocol
Learning Objectives
4
 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
Learning Objectives
4
 Define and create scope options
 Authorize a DHCP server in Active Directory
 Configure DHCP for integration with DNS
 Manage, monitor, and troubleshoot DHCP
Overview of DHCP
4
 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
DHCP Lease Process
4
 Discover
 Offer
 Request
 Acknowledgment
Step 1: DHCPDiscover
4
Step 2: DHCPOffer
4
Step 3: DHCPRequest
4
Step 3: DHCPRequest
4
4
Step 4:
DHCPAcknowledgment
DHCP Renewal Process
4
Configuring a Windows 2000 Server
with the DHCP Server Service
4
1. Configure a static IP address, subnet mask, and
default gateway on the server
2. Install the DHCP server service
3. Create scopes and, if needed
4. Create and specify options on a server
5. Authorize the DHCP server in Active Directory
4
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
4
Client Configuration for
DHCP
Installing the DHCP Server
Service
4
 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
4
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
Installing DHCP
4
Installing DHCP
4
Installing DHCP
4
 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
4
Router Blocking
DHCPDiscover Packets
4
Configuring a DHCP Server
per Physical Segment
Configuring Scopes
4
4
Items in the
New Scope Wizard
 Name and Description
 IP Address range
 Subnet mask
 Add Exclusions
 Lease duration
 Configure DHCP Options
4
Main Options Used with
DHCP
DHCP and Active Directory
4
 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
Integrating DHCP and DNS
4
 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
Integrating DHCP and DNS
4
Troubleshooting DHCP
4
 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
continued
Troubleshooting DHCP
4
 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