Name Resolution Domain Name System

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

DNS Overview Host names DNS 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 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)

Ways to Perform Host Name to IP Address Resolution

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

DNS Hierarchical Structure

Top-level Domains Organizational domains created by designers of the Internet to simplify the naming and logical structure of the DNS namespace

Second-level Domains and Subdomains 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 Zone of authority DNS zone 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 Primary name servers Secondary 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 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 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 Used within the actual zone files to point to particular resources such as hosts, mail exchangers, and name servers

Resource Records continued

Resource Records

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

Installing DNS Service Prerequisites Static IP address Subnet mask Default gateway Set the domain name suffix on the server

Setting the Domain Name Suffix on the Server

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

Installing DNS Service

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

Installing DNS Service

Configuring Zones for Dynamic Updates By default, standard zones on Windows 2000 DNS servers do not support dynamic registration

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

Configuring Zones for Dynamic Updates

Creating Resource Records Manually

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

Basic Manual DNS Configuration for Windows 2000 Clients

Troubleshooting DNS Use nslookup from the command prompt

Dynamic Host Configuration Protocol Easy IP Dynamic Host Configuration Protocol

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

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

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

DHCP Lease Process Discover Offer Request Acknowledgment

Step 1: DHCPDiscover

Step 2: DHCPOffer

Step 3: DHCPRequest

Step 3: DHCPRequest

Step 4: DHCPAcknowledgment

DHCP Renewal Process

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

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

Client Configuration for DHCP

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

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

Installing DHCP

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

Router Blocking DHCPDiscover Packets

Configuring a DHCP Server per Physical Segment

Configuring Scopes

Items in the New Scope Wizard Name and Description IP Address range Subnet mask Add Exclusions Lease duration Configure DHCP Options

Main Options Used with DHCP

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

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

Integrating DHCP and DNS

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 continued

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