1. System & Network Administration (MCSA & RHCSA)
Lecture 2-3 By Waseem Ahmad
Topic :DNS

2. History OF DNS In 1983 ,during the use of Arpanet
Host File (store on Single pc) .
This is in hierarchical structure.
ZONE
Primary Zone ( Which have writable copy of zone file)
Secondary zone ( which obtain read-only copy of zone file)
Strub Zone ( Copy of Zone contain only authoritative DNS Servers for that zone)
1-Each computer have their own Host File for Name Resolution . In which Like Pc-A CC-Pc.
2-And this Host File contains all those computer entries for all node and computer connected with the networks .
Disadvantages :
3 If One new Pc or Node connected to the one of the network then other pc connected to that network have not entry of that pc until not updated Host File .
4 Internet is expand so speedily so we cant updated so large
So we have central Server and each computer in network have know the address of this server .
Like if we want to open then our computer first goes to that server , This Server have its own database then lookup in its database and give the name to ip resolution .
Hirararical modal and domain .
Itlearning.com is our main server , and we have other server us server Asia, Africa Australia .
Then if Asia server request for resolution of site it goes to our main DNS server and then going back to that server .
So for this we placed and make small child server in every zone , That fulfill the request for that local zone.
Zones:
Each Local DNS server have small database this database that contains entries called the zones .

5. Some Important Commands For DNS