Just assume, if an Internet user with high Speed BSNL Broadband Plan having Unlimited Internet is working on Windows 7 Operating Machine / System, then he has to follow the procedure to change the DNS Name Servers address
Go to Control Panel, then select small icons for display,
Network and Sharing Center,
Change Adapter Settings for your connection, Then you will have a pop up screen,
Select Internet Protocol Version 4 (TCP/IPv4),
Properties - If your system shows Automatic and you are unable to resolve any IP
Manual Settings for giving DNS Details, with below mentioned DNS details for preferred and alternate DNS IP details for BSNL DNS Service which you have to populate with more options as follows
Preferred DNS Server: 218.248.255.212, Alternate DNS Server: 218.248.241.2