DNS stands for Domain name server . It's primary purpose is to convert user friendly names to ip adresses . We have two zones in DNS 1. Forward look-up zone : converts names to ip-addresses .2. Reverse look-up zone : convert ip addresses to name or FQDN .Usually when we configure mail servers we have to configure reverse look-up zone . This zone configuration provides a feature of spam protection in mail servers .Now lets look how it works :1.When a DNS name resolution request is forwarded to a DNS server, the DNS server examines its local DNS cache for the IP address. 2. If the IP address is not in the DNS server's cache, it checks its Hosts file. (Since the Hosts file is a static text file, it is not commonly used.) 3. If the DNS server is not authoritative and configured for forwarding, the DNS server forwards the request to a higher-level DNS server4.If the DNS server cannot forward the request, or if forwarding fails, the DNS server uses its Root Hints file (also known as Cache.dns). The Root Hints file lists the 13 root DNS servers. 5. The root DNS server responds with the address of a com, edu, net, or other DNS server type (depending on the request). 6.The DNS server forwards the request to the high-level DNS server, which can respond with a variety of IP addresses.
dns refers to domain name server.it is basically a table which contains the ip addresses corresponding to each and every url.whenever we hit any url in internet explorer,dns is called and the corresponding ip address is called thus calling the corresponding server.it is used because it is really hard to remember ip addresses of each and every server.thus we remember names easily and no need of remembering ip addresses when we use dns.
it resolves the user frienly web site names into ip addresses.As u cant remember the ip addresses easily,so as u type the web site name in URL n it will be resolve by DNS server.
