How does a DNS resolve an IP address?
DNS is acronym for domain name system. DNS server is used to map a name to an address. The reverse mapping is also similar in DNS.
A DNS client "resolves" an IP address by sending a specially-formatted request to a DNS server. The client has to know the address of one or more DNS servers in advance. The reply from the server may be a direct reply with the IP address associated with the hostname, a referral to another DNS server, or a response indicating the requested name can't be found in DNS.
Typically, the request will ask the server to "recurse", i.e. if it cannot answer the question from it's own local memory, it should go ask other servers on behalf of the client. This behavior helps the local server build up it's own cache of addresses frequently looked up.
Another form of query is called iterative query, where a client machine sends request to a known DNS server , if that DNS server fail to resolve the domain name into a IP then the client sends the request to another DNS and this process goes on and on until it get the required IP resolution by sending sending address resolution request to all its known DNS.If every known DNS fail to give the IP, then client goes to the root domain.