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DNS Tutorial

Example: Let’s say kshounish1, kshounish2, kshounish3, kshounish4, and kshounish5 are the 5 machines in a network, then for communication between each machine, each machine’s /etc/hosts file should have all the five entries of the machine name. Within this small network there would be no problem if you add another machine say kshounish6 in the network. But for this too, the network administrator has to go to each machine, add the kshounish6 in /etc/hosts file and then comeback to the new comer kshounish6 machine and add all the other entries (kshounish1...kshounish5) including its own name also in /etc/hosts file.

But what if the network is setup with say 60 machines and a 61st machine has to be added? Then administrator will have to go to each machine again and write the new machine’s name at /etc/hosts/ file and again comeback and write all the 60 machines name on the 61st machine’s etc/hosts file which is a tedious and time taking job. Thus, it is better to keep a centralized server, where all the ipaddresses will stay and if a new one does enter into the network then the change will have to be done at the server and not on the client’s machine. And a better way of setting that client-server networking concept is having one master server and 3-4 slave servers for it.

DNS Setup

DNS is a concept of client server network so both sides configuration is needed.

Example:

Lets say we have 10 machines -- kshounish1 to kshounish10 with 192.192.192.1 to 192.192.192.10 -- and have decided to make kshounish1 as our DNS master server and kshounish2 as slave server and kshounish3 as another slave server and kshounish4 as slave’s slave server. Why do we need a slave server? Well, it is valuable in case of failure of the master server.

Note: Remember, to setup DNS, we need a domain name, as it understand the FQDN format (Fully Qualified Domain Name). So if we decide that our domain name will be bigleap.com. Then our machine names will be kshounish1@bigleap.com…kshounish10@bigleap.com.

Client configuration steps

1) # vi /etc/host.conf

2) replace Order hosts,bind to Order bind,hosts

3) #/etc/rc.d/init.d/network restart

4) # vi /etc/resolv.conf

press “i” and write

domain bigleap.com

nameserver 192.192.192.1(master server)

nameserver 192.192.192.2(slave of master)

nameserver 192.192.192.3(another slave)

nameserver 192.192.192.4(slave of (8)))

11) nslookup(after the master server daemon is running)