HOW DNS WORKs

Before going to the DNS server concepts , first we are going to Know about the name Systems:

Computer Names :

NETBIOS NAME:

NETWORK BASIC INPUT OUTPUT SYSTEM
NETBIOS NAME IS ALWAYS IN CAPS LETTER

MAX LENGTH : 15 CHARACTERS

TOTAL MAX LENGTH: 16 CHAR

16TH CHA IS HIDDEN AND USED AS A SERVICE CALL.

HOW TO CHECK YOUR NETBIOS NAME?

How to enable/disable netbios over tcp/ip ?

by default your computer name is Netbios name also called full computer name

What is DNS name :  ?
DNS name is a full computer  name used by new os default.

example :   mypc.mydomain.com
this name is called dns name. that is uniquely identified a computer on domain.

DNS name is also called internet names that is used on internet or domain

What is FQDN?

FQDN : is fully qualified domain name , have 2 main parts

netbios name + domain name

example : myserver.domain.local
myserver=netbios name
domain.local = domain name

DNS COMPONENTS:

1: DNS CLIENT SERVICE :

DNS client service is a service that provide resolver service and cache the result of a dns query ,

fetching query from client to dns server for name resolve , and get back the answer for successfully resolve the result.
dns client service is by default started automatically on client os. and also server os.

2: DNS SERVER SERVICE:


dns server service only resides on server o.s.   example - windows 2003/2008 server

dns service is not by default installed , you can install a dns server service using server manager.
if the Active directory is installed , dns is a automatically installed.

Installing a stand alone DNS server.active directory not required.
install a dns server without AD
go to server manager, choose dns and then install


What is dns server do ?dns server is just like  a database or like a telephone directory
a telephone directory store name/address and phone no with a index

a DNS is like that but it is more complex than telephone directory. dns server resolve hostname to respective ip address and vice-versa.

DNS have 2 zones

1: Forward lookup zone: hostname to ip
2: Reverse lookup zone: ip to hostname

forward lookup zone resolve hostname to ip address and reverse lookup   zone resolve ip adress to hostname.

Every Zone contains 3 type of zone:
1:    Primary Zone
2:    Secondary Zone
3:    Stub Zone
you can select any of the zone at a time.

you can not install all 3 zones at athe same server.

primary zone: contains read/write copy of the dns database file. you can install the primary zone if
you have no any zone already installed, means it is mandatory to install primary zone first if you have
install fresh dns server(new),this server called primary dns server.(prefered dns server)

secondary zone: contains read only copy of the Primary zone database file, you can not edit or change
the record on secondary server , it is also called backup copy of the primary server,
    if the primary dns server fails, the  secondary dns server comes to resolve the client request.
so the secondary zone is exist on the secondary dns server.(alternate dns server)

stub zone : contains read only copy of the Primary zone database file, but stub zone contains
limited records also called Glue records(NS,SOA,A) records, that is necessary to authorize the zone,
actualy the stub zone is not itself resove the cilents query, it is works like a pointer to point a active
primary dns server in his list of authoritative server, it is a mediator between primary server and client , first client sends query to dns server that contains stub zone, then dns server sends the client query to the authoritative dns server for resolving the answer of the query.
stub zone speed-up the client query if dns server is not contacting .stub zone server is also a secondary dns server but not a backup purpose.

DNS records types :
DNS records are called Resource records(RR)
1: HOST(A)
2: POINTER(PTR)
3: NAME SERVER (NS)
4: START OF AUTHORITY(SOA)
5: MAIL EXCHANGE (MX)
6: CANONICAL NAME (CNAME) OR ALIAS
7: SERVICE LOCATION RECORDS (SRV)
8:HOST(AAA)
9: HARWDARE INFORMATION (HINFO)