How DNS Resolution Works

What is DNS and Why Name Resolution Exists

Computers do not understand names like google.com.
They understand numbers (IP addresses) like 142.250.190.14.

👉 DNS (Domain Name System) converts:

google.com → IP address

Simple analogy

Phonebook

• Name → Phone number

• Website name → IP address

Without DNS, you would have to remember IPs for every website.

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What is dig and Why It Is Used

dig means Domain Information Groper.

It is a command-line tool used to:

• check DNS records

• see which servers answer DNS queries

• understand how name resolution happens

👉 Browsers use DNS silently.
👉 dig lets humans see it.

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DNS Works in Layers

DNS resolution happens in levels:

Root Server
   ↓
TLD Server (.com, .org)
   ↓
Authoritative Server (google.com)

Each level gives directions, not the final answer (until the end).

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1️⃣ dig . NS → Root Name Servers

Command:

dig . NS

What this means

• . means root of DNS

• NS means name servers

What you learn

👉 This shows root name servers
👉 Root servers know:

“Who handles .com, .org, .net?”

📌 Root servers do not know IPs of websites
They only give directions.

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2️⃣ dig com NS → TLD Name Servers

Command:

dig com NS

What this means

• Asking: “Who manages .com domains?”

What you learn

👉 These are TLD (Top Level Domain) servers
👉 They know:

“Which name servers are responsible for google.com, amazon.com, etc.”

Still no IP yet.

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3️⃣ dig google.com NS → Authoritative Name Servers

Command:

dig google.com NS

What this means

• Asking: “Who is the boss for google.com DNS?”

What you learn

👉 These servers are authoritative
👉 They own the DNS records for google.com

They know:

• A record

• MX record

• CNAME

• everything about google.com

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4️⃣ dig google.com → Final Answer (IP Address)

Command:

dig google.com

What happens internally

1. Ask root → where is .com?

2. Ask .com → where is google.com?

3. Ask authoritative server → what is IP?

4. Get IP address ✅

👉 This is the full DNS resolution flow.

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How Browser Uses DNS (Real Life)

When you type:

google.com

Your browser:

• asks a recursive resolver (ISP / Google DNS)

• resolver does all root → TLD → authoritative work

• browser gets IP

• browser connects to server

You never see this — but dig shows it.

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What NS Records Mean (Very Simple)

NS record = Who is responsible for this domain

Example:

google.com → ns1.google.com

👉 It tells:

“Ask this server for answers about this domain.”

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Mental Model :

Think of DNS like asking directions:

• Root → “Go to .com office”

• TLD → “Go to Google office”

• Authoritative → “Here is the exact address”

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Simple Diagram

Browser
  ↓
Recursive Resolver
  ↓
Root Server
  ↓
TLD Server (.com)
  ↓
Authoritative Server (google.com)
  ↓
IP Address