DNS ( Domain Name Service/Domain Name System )

What is DNS?
􀂇 Domain Name Service/Domain Name System
􀂇 Provides resolution of names to IP addresses and
resolution of IP addresses to names
􀂇 Defines a hierarchical namespace where each level of
the namespace is separated by a “.”

What is a DNS Server?
􀂇 Computer running DNS service
Can be:
􀃭 Microsoft® Windows® Server 2003
􀃭 Windows 2000
􀃭 Microsoft Windows® NT 4
􀃭 UNIX
􀃭 Linux
􀃭 NetWare Etc.

DNS Namespace:-Ex:- corporate.Microsoft.com

Authoritative & Non-authoritative DNS server
􀂇 Authoritative DNS server:-
An authoritative DNS server will either:
􀃭 Return the requested IP address
􀃭 Return an authoritative “No”
􀂇 Non-authoritative DNS server
An Non-authoritative DNS server will either:-
􀃭 Check its cache
􀃭 Use forwarders
􀃭 Use root hints

Lookup Types
􀂇 Forward lookup
Requests Name-to-IP Address resolution
􀂇 Reverse lookup
Requests IP Address-to-Name resolution

Fully Qualified Domain Name (FQDN)
􀂇 Identifies a host’s name within the DNS namespace hierarchy
􀂇 Host name plus DNS domain name = FQDN
Ex:- dotnet2003.dot.com

ZONE in DNS ?
Zone is a storage database which contains all
zone Records
􀂇 Forward Lookup Zone
􀃭 Used for Resolving Host Names to IP-Address
􀃭 It maintains Host to IP Address Mapping Information
􀂇 Reverse Lookup Zone
􀃭 Used for Resolving IP-Address to Host Names
􀃭 It maintains IP Address to Host Mapping Information

Types of Records in DNS ?
􀂇 SOA Record
􀃭 The first record in any zone file
􀂇 N S Record
􀃭 Identifies the DNS server for each zone
􀂇 Host Record
􀃭 Resolves a host name to an IP address
􀂇 Alias Record
􀃭 Resolves an alias name to a host name
􀂇 Pointer Record
􀃭 Resolves an IP address to a host name
􀂇 MX Record
􀃭 Used by the mail server
􀂇 SRV Records (Service Record)
􀃭 Resolves names of servers providing services

Zone Types

􀂇 Standard Primary
It is the Master Copy of all the Zone Information.
It is Read/Write copy
􀂇 Standard Secondary
It is Backup to Primary zone. It is Read Only
􀂇 Stub Zone
It contains only NS ,SOA & possibly Glue (A) Records
which are used to locate name servers
􀂇 Active Directory Integrated
It stores the information of Zone in ACTIVE DIRECTORY
DATABASE

Roles of DNS Server
􀂇 Standard Primary
􀂇 Standard Secondary
􀂇 Stub Zone
􀂇 Active Directory Integrated
􀂇 Cache Server
􀂇 ROOT Server
􀂇 Forwarders

What are Service Records?
􀂇 SRV records allow DNS clients to locate TCP/IP-based
Services.
􀂇 SRV records are used when:
􀃭 A domain controller needs to replicate
􀃭 A client searches Active Directory
􀃭 A user attempts to change her password
􀃭 An administrator modifies Active Directory