The DNS works on a question-answer model.
Assume that you have entered "test.ru" into the browser line.
Let's take a look at DNS operation step-by-step:
- Your browser knows nothing about "test.ru" IP address and it sends a request on IP address (through a special program — resolver) to the local name server. Local DNS server is a name server of your local network or DNS server of your Internet provider. One may ask: "How does the browser know about availability of such local DNS ?" It's very simple. At setting the network connection it shall be necessary to indicate IP addresses of DNS servers (preferred and/or alternate), one of which will be responding to requests sent by your browser through the resolver. This is actually the local server of your network. You will always be able to view IP address of your local DNS server. This can be done by opening the properties of network connection used by your PC.
- A request to find out the IP address of test.ru is received by the local name server. The server knows nothing about this IP address and sends a request to one of the root servers "." .
- The root server gives to the local server an IP address of the server which supports .ru domain.
- Then, the local name server calls (using the received address) DNS server which supports .ru.
- Upon receipt of the request the DNS server, in its turn, provides IP address of the server which supports "test.ru" domain.
- The local DNS server sends a request to find out test.ru IP address to DNS server of test.ru zone.
- The local name server receives test.ru IP address from DNS server of test.ru zone.
- Having received the test.ru address, the local DNS server sends this information to your browser.