Covering Essentials (Core Concepts.)
1. What DNS is (explained in very simple terms)
Lets Understand & Decode This Image So That We Can Understand What Happens Behind The Scene.
Think Of DNS As Your Friends Home What Will You Do When You Need To Find The Friends Home You Ask Him / Her Address Same Is DNS It Looks Up The Address That You Are Searching for.
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Now Explaining The Image.
1. User
The user types example.com in the browser.
The user only knows the website name, not the IP address.
2. Recursive DNS Resolver
This is the first server that receives the request.
Its job is to find the IP address for the user.
3. Root DNS Server
The resolver asks the Root DNS server about example.com.
The root server replies with where the .com information is stored.
4. .com TLD Name Server
The resolver now contacts the .com TLD server.
This server tells which server has the final details of example.com.
5. Authoritative DNS Server
This server knows the exact IP address of example.com.
It sends the correct IP back to the resolver.
6. IP Address (192.0.0.16)
The resolver sends the IP address to the user.
The browser uses this IP to load the website.
2 . Why DNS records are needed
Generic Example.
Think of DNS records like notes saved in a contact.
Each note tells something different about that person.
1. Website address mapping
DNS records connect a domain name to its IP address.
Without this, the browser won’t know where the website is hosted.
2. Email routing
Some DNS records tell where emails should be delivered.
This ensures emails reach the correct mail server.
3. Handling multiple services
One domain can be used for website, email, and APIs.
DNS records help route traffic to the correct service.
4. Load balancing and reliability
DNS records can point to multiple servers.
This helps distribute traffic and avoid server overload.
5. Security and verification
Some records are used for verification and security.
They help prevent fake emails and unauthorized access.
3 . What an NS Record is (who is responsible for a domain)
Once We Decode The Image We Clearly Would Be Understanding How NS Works.
Think of a company manager.
He handles main work but assigns different teams to handle specific tasks.
1. Authoritative DNS server for example.com
This server controls the main domain example.com.
It decides who should handle the subdomains.
2. Delegating blog.example.com
The main DNS server gives control of blog.example.com to Server A.
Server A now answers all DNS queries for the blog.
3. Delegating mail.example.com
The main DNS server gives control of mail.example.com to Server B.
Server B answers all DNS queries related to mail.
4. Role of Server A
Server A has full authority over blog.example.com.
Any DNS request for the blog goes to Server A.
5. Role of Server B
Server B has full authority over mail.example.com.
It manages all mail-related DNS records.
6. Why DNS delegation is used
It helps split control and reduce load on one server.
Different services can be managed separately.
4 . What an A Record is (domain → IPv4 address)
Understand It At Generic Way Then Decode The Image.
Think of a house name and house number.
The name is easy for humans, but delivery works using the number.
1. What an A Record means
A record stands for Address record.
It connects a domain name to an IPv4 address.
2. Domain name column
The name column shows the domain like example.com.
This is the website name users type in the browser.
3. IP Address column
The IP address column shows where the website is hosted.
This is the actual address computers use to connect.
4. Multiple A records
A domain can have more than one A record.
This helps with load balancing and better availability.
5. TTL (Time To Live)
TTL tells how long DNS should cache the record.
Lower TTL means faster updates but more DNS queries.
6. Why A Record is important
Without an A record, the domain cannot point to a server.
The website will not open even if the domain exists.
5 . What an AAAA Record is (domain → IPv6 address)
Lets Understand AAAA Record By An Image Decoding.
Generic Example
Think of adding a new contact in your phone.
You enter the name and save the correct number.
1. Create AAAA Record
This screen is used to add a new AAAA record in DNS.
It is specifically meant for mapping a domain to an IPv6 address.
2. Host Name
The host name field contains values like www.
This means the record is for www.example.com.
3. Destination IPv6 Address
Here you enter the IPv6 address of the server.
This is the actual location where the website is hosted.
4. IPv6 address format
IPv6 addresses are longer and use hexadecimal values.
They look different from IPv4 but work the same way.
5. Add New DNS Record
Clicking this button saves the AAAA record.
DNS will now know where to route IPv6 traffic.
6. What happens after saving
DNS updates take some time to propagate.
Once done, the website becomes reachable over IPv6.
6 . What a CNAME Record is (one name pointing to another name)
Lets Decode The Cname Using Image.
Generic Example.
Think of a nickname pointing to your real name.
Different names, but they finally mean the same person.
1. A record for main domain
The main domain example.com points to an IP address using an A record.
This IP is where the actual server is located.
2. CNAME for www.example.com
The www.example.com does not have its own IP.
It points to example.com using a CNAME record.
3. How DNS resolves it
When someone opens www.example.com, DNS follows the CNAME.
Then it checks the A record of example.com to get the IP.
4. CNAME for cdn.example.com
The cdn.example.com points to another domain name.
This is commonly used for CDN or external services.
5. Name-to-name mapping
CNAME always points one name to another name.
It never points directly to an IP address.
6. Why CNAME is useful
You manage the IP address in only one place.
All linked names automatically follow the change.
7 . What an MX Record is (how emails find your mail server)
We Can Decode The MX (MAIL EXCHANGE) Record Using The Image Above.
Generic Way.
Think of sending a parcel.
You first find the correct post office, then delivery happens.
1. Sender sends an email
The sender sends an email to hello@example.com.
The sender’s mail server starts the delivery process.
2. MX request to DNS
The sender mail server asks DNS for the MX record of example.com.
It wants to know where emails for this domain should go.
3. DNS server response
DNS replies with the mail server name for example.com.
It also provides the IP address of that mail server.
4. Receiver mail server
The mail server mail.example.com receives the email.
This server is responsible for handling incoming mails.
5. Email delivery to recipient
The receiver mail server delivers the email to the recipient.
The email now appears in the user’s inbox.
6. Why MX record is important
MX records guide emails to the correct mail server.
Without them, emails would never reach the inbox.
8 . What a TXT Record is (extra information and verification)
We Will Understand TXT(TEXT) What Does It Do How It Works.
Generic Example
Think of writing a secret note for verification.
Only the correct person can read and verify it.
Let’s Decode The Image.
1. Record type
The record type is set to TXT Record.
This tells DNS that text information is being added.
2. Host name
The host name shows default._domainkey.
This is commonly used for DKIM email verification.
3. Text value
The text field contains a long string.
This string is used for verification and security.
4. DKIM information
This TXT record stores DKIM data.
Mail servers use it to verify genuine emails.
5. Time To Live (TTL)
TTL defines how long DNS should cache this record.
Lower TTL allows faster updates.
6. Adding the record
Clicking Add Record saves the TXT entry.
DNS will now use this information for verification.
9 . How all DNS records work together for one website
This Is FInal Concept Where All Our Knowledge Combine & Understand The Flow.
Let’s Decode The Image.
Generic Example
Think of asking for a shop address.
You ask around step by step until you get the exact location.
1. End User
The user opens a browser.
They want to visit a website.
2. User enters website name
The user types www.example.com.
The computer does not know the IP yet.
3. DNS Resolver contacts Root DNS
The DNS Resolver asks the Root Name Server.
Root replies where the .com servers are.
4. Resolver contacts .com TLD server
The resolver now asks the .com TLD server.
It replies with the authoritative name server location.
5. Resolver contacts Authoritative Name Server
The resolver asks the Amazon Route 53 name server.
This server knows the exact IP address.
6. IP address is returned
The authoritative server sends back the IP 192.0.1.100.
The resolver now has the final answer.
7. IP sent to the user
The DNS resolver sends the IP to the user’s computer.
Now the browser knows where the website is.
8. Browser contacts web server
The browser sends a request to http://www.example.com.
It directly contacts the web server using the IP.
9. Website loads
The web server sends the web page back.
The user sees the website on the screen.