DNS SERVER (Domain Name System)

DNS Concept

DNS in Workgroup

DNS in Domain

DNS with DHCP

DNS with A.D

DNS with WINS

DNS with IIS

DNS in LAN

DNS in WAN

DNS Concept

The DNS stands for Domain Name System. It works on 53 no. port. DNS is used to resolve name to IP address of the host computer. DNS is also called Database which stores host records. DNS is available in Windows Server 2000 and Windows Server 2003 operating system.

                                    DNS is introduced in 2000 with Window Server 2000. Domain Name is Hierarchal Structure. It can be use twice time in network.

Difference between NetBIOS Name and Domain Name

NetBIOS Name                                 Domain Name

(1) It is 15 characters long.                             (1) It is 255 bytes long.

(2) It must be unique in the Network.            (2) It will use more than one

     time in the network.

(3)It has flat structure means no sub               (3) It is Hierarchal structure ,

NetBIOS Names.                                              means roots, top level

                                                                          Domains, second level

                                                                          Domains and host

                                                                           Computers.

(4)The primary method to resolve                   (4) The primary method to

NetBIOS over TCP/IP is WINS                       resolve name to IP address

Server in previous Win 2000.                           of the host computer is

                                                                                      DNS Server.

                        

DNS Lookup Types: -

By default, DNS has two Lookup types

(i)                 Forward Lookup

(ii)             Reverse Lookup

(i)     Forward Lookup

The forward lookup is used to store zones, which are responsible for resolve name to IP address of the Host computer. Under forward lookup type, we can create or store Primary Zone, Secondary Zone, and Stub Zone.

(ii) Reverse Lookup

Reverse lookup is used to resolve IP address to name of the Host computer. This is very rarely configure because mostly it is used for in troubleshooting purpose in the NS Lookup.

Zone Types: -

DNS has three types of zones

(i) Primary Zone

(ii) Secondary Zone

(iii) Stub Zone

(i) Primary Zone

In DNS server, we have to create zones under forward lookup type to configure the DNS server. Zone is also called Database, which stores Host records of the computer (NetBIOS Name and IP address). Primary Zone has read and write access. We can update data directly in this zone. This zone is available on first DNS server in the network or we can say this Zone is available on Primary DNS server. It keeps original data. This zone is also responsible for store Host records and resolve name to IP address.

(ii) Secondary Zone

      This zone is also available under the forward lookup type. We can configure this kind of zone on secondary DNS server. It has read only access. You can not update data directly on this zone. It has copy of Primary zone. We can configure secondary DNS server with Secondary zone for the purpose of fault tolerance.

For e.g:- we can configure secondary DNS server with secondary zone with Additional Domain Controller. Zone and Data is replicated from Primary DNS server to secondary DNS server by using zone transfer option process. It keeps copy of Primary original data or Primary zone.

(iii) Stub Zone

       Stub zone does not provide any kind of service like Primary and Secondary zone. It stores special kind of records like NS record (Name of Server) and SOA record (Start of Authority).

Records types:-

(i)                 A Record [Host Record]

(ii)               Alias Record ( c Name )

(iii)             MX Record [Exchange server, Mail server, @domain name (e-mails) ]

(iv)             NS Record  -  Name of Server

(v)               SOA Record  - Start of Authority

(vi)             SRV Record  - Service Location Record

Installation of DNS Server

(1)     log on as a Administrator

(2)     go to control panel -> Add/Remove Programs -> Add/Remove Components -> Network Services -> then click on Detail button -> then check the check box of DNS.

(3)     Click ok.

(4)     Click next to install the DNS server.

You can access DNS server from Administrator Tools.

DNS Suffix

(1)    Registration (Dynamic)

(2)    Query to DNS by client

(3)    DNS respond back to requesting client

(4)    Client communicate with other client

DNS Suffix is used to resolve Name to IP Address of the Host Computer. It is also used to register Host Records of the client computers in DNS server dynamically.

            In real means DNS Suffix is the name of the Primary Zone configured in the Primary DNS server.

Steps to assign DNS Suffix

(1)     Log on as Administrator.

(2)     Configure TCP/IP. IP Address, Subnet Mask and Preferred DNS IP Address.

(3)     Now right click on My Computer icon then Properties -> Computer Name Tab -> Change button -> More button.

(4)     In the Primary DNS Suffix text box. Type the name of the DNS Suffix.

(5)     Click ok and restart your computer.

To make member of DNS

On workgroup computer, Fill Suffix name of Domain and Restart PC or type command on Command Prompt C:\>ipconfig/registerdns.

Dynamic Updates

Dynamic Updates are updates which are registered in DNS server dynamically. Here Dynamic updates are Host records of the client computer (Name & IP Address). These updates are registered in DNS server dynamically with the help of DNS Suffix.

            When your DNS server accepting Dynamic Updates then your DNS server is called DDNS (Dynamic DNS).

            We can also set Dynamic Update acceptance behavior of the DNS server, in which we have three options:-

(i) Secure only

     In this option only active directory clients can register their Host Record in DNS server.

(ii) Secure and Non-Secure only

In this option active directory clients and workgroup clients, Both can able to register their Host record in DNS server.

(iii) Do not Allow

  In this option no one can register their Host record in DNS server.

      You can also change these options by zone properties.

DNS with Active Directory

DNS server plays a very important role in Domain Environment. We can also say Active Directory is tightly integrated with DNS server or DNS is a backbone of Active Directory. DNS work without Active Directory in workgroup environment. But Active Directory can not work without DNS server.

            When we install Active Directory with DNS server then A.D registers its Domain Name in DNS server, when we join clients in Domain Environment then we have to provide IP Address of the DNS server to our client computers. First request goes to DNS server. DNS server locates the Domain Controller and the request shifted to Active Directory. So in this way client computers join Domain environment.

Protocol/Port No.

=> Protocol used in Active Directory is LDAP (Light Weight Directory Access Protocol) and the Port no. is 389.

=>In Domain environment the authentication protocol is KERBROS and the Port no. is 88.

                        (also check clock synchronization)

DNS with WAN

Top level Domain

.Com

.Edu

.Net

.Co.in

.Org

.Ca

.Uk

.Mil

Root Server

We have 13 Root servers. This is available on the top of the Hierarchal Structure in Domain Name System. Microsoft provides the name & IP Address of Root Servers in the DNS server.

                        When a DNS server receives a query from a client, First of all, it will try to resolve the query. if it has no answer then DNS server go to Root server on the Internet by using Root Hints (List of Name & IP Address of Root Servers).

Query Type

(1) Recursive Query

(2) Iterative Query

(3) Referral Query

(4) MX Query

(1) Recursive Query

      Client to DNS

(2) Iterative Query

      DNS performs query on behalf of its clients.

(3) Referral Query 

      Appro: answer provided by Root and Com.

When client receives proper answer from DNS Server then one Recursive Query is completed. The whole process which is performed on behalf of client is called Recursion. By default, Recursion option is enabled in DNS server.

(4) MX Query

      Which Query solved about mail that is MX Query.

Types of DNS Server

(1) Primary DNS Server

(2) Secondary DNS Server

(3) Cache Only DNS Server

Primary DNS Server

This is a first DNS Server in the network. It contains original data. It has Primary Zone under forward lookup.

Secondary DNS Server

This is a second DNS server in the network also act as a Backup Server. We can also say Secondary DNS server is used to provide fault tolerance in the network. It has Secondary Zone under the Forward Lookup Zone and Data is replicated from Primary to Secondary DNS server by Zone transfer process. It has read only access. Secondary DNS server queried to its master server for new updates after every 15 minutes.

Cache Only DNS server

This is the type of DNS server. It has no Zone. But it has Cache, Root Hints and one another thing Forwarders.

                        There is no additional configuration required in Cache Only server. We will just install DNS role in the computer. We can use it for two purposes:-

(1) Internet use

   

     Server side configuration 

     In this process no additional configuration required. But Internet connectivity required.

      Client side configuration

       In PDNS IP Address, we will provide IP Address of Cache Only DNS server.

(2) Between two offices

      (Branch office and Head office)

     But in this case we have to configure Forwarders. In which we will provide Domain Name and IP address of DNS server, Which is responsible for this Domain Name Zone.

C:\>ipconfig/flushdns

Clear your cache and read the correct information from your DNS.