How DNS Resolution Works
What Happens Under the Hood?
I build clean and simple web experiences and learn something new every day.
Have you ever wondered what actually happens when you type google.com in your browser and press Enter?
How does you browser know where to take you? Why doesn’t it send you to some random website? And most importantly how does the internet understand human readable names like google.com?
This blog is my attempt to understand DNS from absolute basics to a professional leel mental model, written exactly the way I learned it step by step, no assumptions, no jargon overload.
1. The Question That Started It All
when I type:
google.com
into my browser, I’m not giving it:
a location
a server address
or any networking details
Yet somehow, I always land on Google, and not somewhere else.
So the obvious question is:
How does my browser know where to go?
The short answer is DNS. The real answer is much more interesting.
2. Why DNS Exists
Computer do not understand domain names. They communicate using IP addresses, like:
142.250.195.46
Imagine if every time you wanted to visit a website, you had to remember numbers like these. That’s not realistic right.
This is Why Name Resolution Exists
Name Resolution exists to solve one problem:
Convert a human-friendly name into a machine-friendly IP address.
That conversion system is called DNS (Domain Name System).
3. DNS= Internet’s PhoneBook (But Smarter)
I like to think of DNS as:
The internet’s phonebook
| Real World | Internet |
| Person’s name | Domain name (google.com) |
| Phone number | IP address |
| Phonebook | DNS |
But unlike a draditional phonebook:
DNS is distributed
DNS is hierarchical
DNS is globally scalable
4. What Happens When I Search google.com?
Here’s the important part:
My browser does NOT directly ask Google.
Instead, it asks:
Hey, does anyone know the IP address for
google.com?
That question starts a multi-step journey through DNS.
5. DNS Works in Layers
DNS resolution doesn’t happen in one step. It happens layer by layer.
DNS Hierarchy
Each layer only knows who to ask next.
6. Before Going Deeper: What is the dig Command?
While learning DNS, I realize I needed a way to see DNS in action. That’s where dig comes in.
What is dig?
dig (Domain Information Groper) is a DNS inspection tool.
It allows us to:
Ask DNS questions manually
See which servers respond
Understand resolution step by step
Think of it as debugging DNS.
7. Why I Use dig
I don’t use dig to browse the internet. I use it to:
Learn how DNS works
Debug DNS issues
verify name server configuration
Build a system-design-level understanding
8. Understanding NS Records
While exploring DNS, one term keeps appearing:
NS (Name Server) Records
An NS record answers one simple question:
Who is responsible for this domain?
Important:
NS records do not give IP addresses
They tell where to ask next
This is how DNS stays scalable.
9. Starting from the Top: Root Name Servers
Command
$ dig . NS
;; QUESTION SECTION:
;. IN NS
;; ANSWER SECTION:
. 395484 IN NS a.root-servers.net.
. 395484 IN NS b.root-servers.net.
. 395484 IN NS c.root-servers.net.
. 395484 IN NS d.root-servers.net.
. 395484 IN NS e.root-servers.net.
. 395484 IN NS f.root-servers.net.
. 395484 IN NS g.root-servers.net.
. 395484 IN NS h.root-servers.net.
. 395484 IN NS i.root-servers.net.
. 395484 IN NS j.root-servers.net.
. 395484 IN NS k.root-servers.net.
. 395484 IN NS l.root-servers.net.
. 395484 IN NS m.root-servers.net.
This asks:
Who handles the root of DNS?
What Root Servers Do
They sit at the top of DNS hierarchy
They don’t know website IPs
They only point to TLD servers
Mental Model
I don't know google.com,
but I know who manages .com
10. Next Layer: TLD Name Servers
Command
$ dig com NS
;; QUESTION SECTION:
;com. IN NS
;; ANSWER SECTION:
com. 171633 IN NS e.gtld-servers.net.
com. 171633 IN NS h.gtld-servers.net.
com. 171633 IN NS l.gtld-servers.net.
com. 171633 IN NS a.gtld-servers.net.
com. 171633 IN NS c.gtld-servers.net.
com. 171633 IN NS j.gtld-servers.net.
com. 171633 IN NS f.gtld-servers.net.
com. 171633 IN NS k.gtld-servers.net.
com. 171633 IN NS b.gtld-servers.net.
com. 171633 IN NS d.gtld-servers.net.
com. 171633 IN NS g.gtld-servers.net.
com. 171633 IN NS m.gtld-servers.net.
com. 171633 IN NS i.gtld-servers.net.
TLD stands for Top-Level Domain.
Examples:
.com.org.in
What TLD Servers Do
They answer:
Who is authoritative for
google.com?
They don’t give the IP yet. They just point forward
11. Final Authority: Authoritative Name Servers
Command
$ dig google.com NS
;; QUESTION SECTION:
;google.com. IN NS
;; ANSWER SECTION:
google.com. 49892 IN NS ns4.google.com.
google.com. 49892 IN NS ns2.google.com.
google.com. 49892 IN NS ns1.google.com.
google.com. 49892 IN NS ns3.google.com.
These servers:
Own the DNS data for the domain
Store actual records
Are the source of truth
Only authoritative servers return the ffinal IP address.
12. The Full DNS Resolution Flow
Command
$ dig google.com
;; QUESTION SECTION:
;google.com. IN A
;; ANSWER SECTION:
google.com 262 IN A 142.250.206.14
Behind the scenes, this is what happpens:
1. Browser → Recursive Resolver
2. Resolver → Root Server
3. Root → TLD Server (.com)
4. TLD → Authoritative Server
5. Authoritative → IP Address
6. Resolver → Browser
13. Recursive Resolver: The Hidden Worker
I don’t manually query root or TLD servers.
A recursive resolver does it for me.
Examples:
ISP DNS
Google DNS (8.8.8.8)
Cloudflare (1.1.1.1)
It:
Queries DNS layers
Caches results
Speeds up browsing
14. Mapping dig to DNS Layers
| dig Command | DNS Layer |
dig . NS | Root |
dig com NS | TLD |
dig google.com NS | Authoritative |
dig google.com | Full Resolution |
This mapping helped me visualize DNS clearly.
15. How This Connects to Real Browsing
Every time I open a website:
DNS resolution happens
IP address is found
Network connection starts
Website loads
DNS is always the first step.
16. Why DNS Is Designed This Way (System Design View)
DNS is:
Distributed → No single failure
Hierarchical → Scales globally
Cached → Fast
Stateless → Reliable
This same thinking appears in modern system design.
17. Final Thoughts
DNS felt mysterious at first. But once I broke it down layer by layer, it became logical.
Now when I type google.com, I don’t see just a website I see a well-orchestrated distributed system at work.