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 220.127.116.11 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
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.
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.
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
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