Domain Name Servers (DNS) are the Internet’s equivalent of a phone book. They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses. This is necessary because, although domain names are easy for people to remember, computers or machines, access websites based on IP addresses.
DNS Port Number is 53
Types of Lookups in DNS: Forward DNS is a type of DNS request in which a domain name is used to obtain its corresponding IP address. A DNS server is said to resolve a domain name when it returns its IP address. A forward DNS request is the opposite of a reverse DNS lookup. Forward DNS is also known as a forward DNS lookup.
In this figure, User Request to google.com its checking in local server and its forward to Public Domain, getting Response form Public domain server.
Conditional Forwarder
A conditional forwarder is a Domain Name System (DNS) server on a network that you use to forward DNS queries according to the DNS domain name in the query.
In this figure, we seeing trust relationship between windowstechpro and Techpro.