DNS: Domains, Records, and How the Internet Knows Where to Go ?

What is DNS?

The Domain Name System (DNS) is like the phonebook of the internet. While humans remember domain names like google.com, computers use IP addresses like 142.250.64.78. DNS maps these names to their respective IP addresses, allowing us to use readable names to access websites, apps, and services.

What is a Domain?

A domain is your website’s readable address. It typically includes:

• Top-Level Domain (TLD): .com, .org, .net, etc.

• Second-Level Domain: The actual name (e.g., google)

• Combined: google.com

You can also have subdomains like:

• www.google.com

• mail.example.com

• api.myapp.io

DNS Structure: How It Works

1. You enter a domain in your browser.

2. Your device asks a DNS resolver (usually from your ISP).

3. The resolver queries authoritative DNS servers until it finds the IP address for the domain.

4. Your browser connects to the IP and loads the website.

This entire process usually takes milliseconds.

Common DNS Record Types

DNS records are instructions stored in the DNS zone file of your domain. They define how your domain behaves and where it should point.

1. A Record (Address Record)

• Points a domain/subdomain to an IPv4 address.

• Example:

    Host: @
    Type: A
    Value: 192.0.2.1
  

  This means example.com goes to IP 192.0.2.1.

2. AAAA Record

• Same as A record, but for IPv6 addresses.

• Example:

    Host: @
    Type: AAAA
    Value: 2001:db8::1
  

3. CNAME (Canonical Name Record)

• Maps one domain to another domain name.

• Cannot be used at the root domain (@).

• Example:

    Host: www
    Type: CNAME
    Value: yourapp.netlify.app
  

4. ALIAS / ANAME

• Works like a CNAME but can be used at the root domain.

• Resolves to an IP address behind the scenes.

• Used by providers like AWS Route 53, Cloudflare, etc.

5. MX (Mail Exchange Record)

• Directs email to your mail servers.

• Example:

    Host: @
    Type: MX
    Value: mail.example.com
    Priority: 10
  

6. TXT (Text Record)

• Used for human-readable or machine-verifiable text.

• Often used for:

  • SPF/DKIM/DMARC (email security)

  • Domain verification (e.g., Google Search Console)

• Example:

    Host: @
    Type: TXT
    Value: "v=spf1 include:_spf.google.com ~all"
  

7. NS (Name Server Record)

• Specifies which name servers are authoritative for the domain.

• Changing this transfers DNS control to another provider.

8. PTR (Pointer Record)

• Used for reverse DNS lookups (IP → domain).

• Typically configured by your hosting provider.

Special Host Symbols

When to Use Which Record?