DNS (Domain Name System) Zones & Delegations

DNS zones and delegations are important concepts to learn in order to properly implement a DNS domain. I’m going to explain Zones & Delegations with illustrations, We know that DNS is a hierarchical structure so let’s take analogy of an organization “XYZ”. We can say a DNS Zone is an Organizational area of a domain.

The “XYZ” organization is divided up to three major departments HR, Engineering and Marketing which are further divided into sub-sections or departments.

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DNS Zones and Delegations

In the above illustration you can see the head of organization XYZ is “Steve” which delegates off the responsibilities to different departments.

HR is heading by Smith but HR is big department so Smith hired Frank and Joe to run those sub departments.

Same like Jerry is managing whole Engineering department but Dev and Test is being managed by Bill and Phil.

You can see the yellow circle around jerry which covers Bill and Phil because Jerry only needs to know about the top managers so Jerry can get information from Bill and Phil if he need to know something under Web and Mobile department.

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DNS Zones and Delegations

For example, Mr. Unknown calls to Mr. Steve and asks for Stacy in Engineering department so then Mr. Steve will look into his directory which contains top heads of department and route call to Jerry which is heading the Engineering department.

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DNS Zones and Delegations

You can see the Jerry’s zone is overlapping with Bill that means Jerry is also responsible for Bill’s Dev department.

Similarly the real world DNS Zones work by delegating the responsibilities to their subordinates.

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DNS Simulation

There are root DNS “.” servers which reside on top of hierarchy so they know about Top Level Domains (.com, .net, .org, .ai). A server which hosts a domain namespace or zone called Name Server.

Download here DNS Simulation lab for Cisco Packet Tracer.



Is “WWW” a top level domain or subdomain?

WWW is a subdomain.

If .com, .org, .net are top level domains then what are .com.us?

.us is the country code top-level domain (ccTLD) for the United States

How many types of DNS Queries for name resolution?

Recursive and Iterative Queries.

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