Introduction to the concepts of Domain Name Service (DNS)

When we start to learn about network administration, one of the most important services is Domain Name Service(DNS). Today we are going to get an introduction and a look at some of the most important concepts that you need to know before hand.

What is DNS?

DNS stands for Domain Name Service: This is the process of resolve full qualified name(FQDN) like www.example.com into IP addresses like 128.10.10.10 and IP addresses into FQDN

DNS is compound of Zones and Records. 
A zone is a domain name that holds different records while a record is a pointer to a specific address or device

DNS is a service that runs by default on a client computer, this is call Client DNS. To have a DNS server you will need a Server OS(Operative System) and the DNS server application. (DNS is call bind on Linux systems)

Roles of DNS

Primary: Contains a Read/Write copy of the zone database

Secondary: Contains a Read-only copy of the primary server zone database

Master: A server that provides a copy of the zone database to a secondary

Slave: A server that receives a copy of the zone database from a master

DNS Roles Example
DNS Roles Example
Zones

There are 2 main kind of zones:

Forward Look up Zone: Resolves names to ip addresses through the records on its zones.

Reverse Look up Zone: Resolves IP addresses into FQDN through ptr records.

Records

There are different kind of records:

SOA(Start Of Authority): Is perhaps the most important of all records on a zone. Points to the primary zone, list the time to leave for the zone, have a serial number that increments every time a change is made in the zone.

NS(Name Server): Identifies who is holding the records of the domain or subdomain, normally points to a DNS Server.

A(Host): Allows the assignation of names to an ip address like                  www —> 192.168.1.25

PTR(Point to Record): Used on a reverse look up zone, does the inverse of an A record. Example: nslookup 192.168.1.25 —> www

CNAME(Canonical Name) or alias: Allows a host to be resolve by different names.

dns-cname-example
CNAME Example

 

 

 

MX(Mail Exchange): Resolves  where a mail server is located to redirect emails to it.

SRV(Service Location): Some applications or services uses this type of records, and example of it is Active Directory.

Watch this video with a full explanation of all this

wanna know more?

Technet DNS

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