Understanding DNS Record Types.

How does a browser know where the website lives?

• When you type google.com the browser don’t know where is this website is.

• Computers can’t understand website names, they only understand IP addresses like 142.250.190.14.

• So when you type domain name goole.com, browser needs an IP address to find that IP address DNS helps.

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What is DNS

• DNS(Domain Name System) is a distributed system that maps human-readable domain names into IP addresss , it acts like internet phonebook .

• Humans like to use names because they are easy to remember and Computer like to use numbers because they understand numbers, DNS connects these two.

Why DNS records are needed

• DNS by itself is just a system, to actually work, it needs information, that information is stores using DNS records.

• A single website needs different kinds of information like where is the website lives, who controls the domain, where email should go, extra verification data.

• One type of record can’t store all this.

• So DNS uses different record types, each with a specific job.

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What is NS record

• NS(Name server) record tells the internet which DNS authoritative servers are responsible for a domain.

• An NS record tells which authoritative DNS servers manage a domain.

• When you search google.com → DNS resolver reaches TLD server .com → TLD server checks the NS records → NS record tells where the authoritative DNS server is → Authoritative server returns the IP address.

• Example:

  1.A user searches google.com

  2.The DNS resolver reaches the .com TLD server
  3.The .com TLD server returns the NS records ns1.google.com, ns2.google.com, ns3.google.com, and ns4.google.com.
  4.The DNS resolver contacts one of the listed NS(Name servers).
  5.That server returns the IP address 142.251.220.46.

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What is an A record

• The A record is stored on the authoritative DNS server, where all DNS records for a domain are kept.

• An A record stores the IPv4 address of website.

• The DNS resolver gets this record from the authoritative DNS server during DNS resolution.

• Example: A record for google.com → 142.250.190.14.

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What is an AAAA record

• An AAAA (Quad-A) record is stored on the authoritative DNS server, along with the other DNS records for a domain.

• An AAAA record stores the IPv6 address of website.

• IPv6 addresses are newer and longer that IPv4 addresses, and IPv6 are used to support the growing number of internet devices.

• During DNS resolution, if a system supports IPv6, the DNS resolver can retrieve the AAAA record to find the website’s IPv6 address.

• Example: AAAA record for google.com → 2607:f8b0:4005:080a::200e .

• A website can have the both A record(IPv4) and AAAA record(IPv6) at the same time.

• Browsers give higher prority to AAAA record (IPv6).

• Browser first asks DNS for AAAA record (IPv6), if IPv6 ia available browser use it, if not browser falls back to A record(IPv4).

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What is CNAME record

• A CNAME (Canonical Name) record is stored on the authoritative DNS server, along with other DNS records for a domain.

• CNAME record don’t store a IP address.

• It points one domain name to another domain name.

• Sometimes, the same website should be accessible using multiple domain names like google.com, www.google.com.

• Instead of storing the IP address multiple times, DNS uses a CNAME record to avoid duplication.

How a CNAME record works

1. A user types www.google.com

2. DNS finds a CNAME record

3. The CNAME points to google.com

4. DNS then looks up the A or AAAA record of google.com

5. The IP address returned

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What is MX record

• An MX (Mail Exchange) record is stored on the authoritative DNS server, along with other DNS records for a domain.

• MX record tells the internet which mail server should receive emails for a domain.

Example: how mx record works

• Let says your domain name is xyz.com

• Your MX record is xyz.com MX 10 mail.xyz.com

• All emails sent to @xyz.com , such as admin@xyz.com , hr@xyz.com .

• should be delivered to the mail server mail.xyz.com.

• The mail server then distributes each email to the correct mailbox.

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What is TXT record

• A TXT record is a DNS record used to store extra information about domain.

• TXT record store text data that is read by machines, not humans.

• TXT records likes Domain verification, Email security, Ownership proof.

Uses of TXT records

1. Domain verifivation: when you connect a service (google, vercel, github, etc) they ask to add a TXT record.
   Ex: abc.com TXT google-site-verification=abc123

2. Email security:TXT record are used to prevent email spoofing, Only these servers are allowed to send emails for abc.com
   Ex: abc.com TXT v=spf1 include:_spf.google.com ~all

How all DNS records work together for one website

• NS(Name server) → finds authoritative DNS server.

• CNAME → Resolve alias (if any).

• A / AAAA → Gets IP address.

• Browser connects to the server.

• MX → finds mail server.

• TXT → helps verify and secure email.

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How DNS actually works