Domain Name Service (DNS) is a Naming service that maps IP addresses and fully qualified domain names to one another. Computers that runs DNS are called name servers.
Here I have installed and configured cache server using forwarder, forward look-up and reserve look-up. In most of the place, we need a reserve lookups. Caching server will not hold any domain names, it will only work as a Pointing server. Before going in depth we need to know about DNS server and how it works.
What is DNS?
Here is an easy way to understand the DNS and how it works.
If we need to access tecmint.com in browser, the system will look for tecmint.com. Here at the end of the .com there will be a (.) so what is this ?.
The (.) represent the namespace Root server, there are total 13 root servers globally available. While we accessing tecmint.com it will ask to name server as per operating system configuration. In Ubuntu, we used to configure the name-server in /etc/resolv.conf, while accessing tecmint.com my browser will ask to root name-servers, if the root name-server don’t have my requested domain information it will cache my requested information and forward my request to (TLD) Top Level Domain name-server, even in TLD name-server my request is not available it will be cached and forwarded to Authoritative name-server.
While the domain registration, our domain registerer will define which authoritative name-server should our domain use. So, authoritative name servers have our domain information’s, while our request reach ANS it will reply for the query that tecmint.com have 18.104.22.168 at the same time it will be cached in Authoritative name-server and send the request back to browser. Every above steps are done within milliseconds.
Hope you got what is DNS now, and how it works. Now let us set up a Caching DNS Server in Ubuntu Server 14.04 LTS.