Skip to content

DNS & Nameservers

This document explains domains, nameservers, hosts, DNS records, and how DNS resolution works.

[Domain Name]
       |
       v
[Nameserver (NS)]
       |
       v
[DNS Records]
       |-- A Record → Points to Hosting Server IP
       |-- CNAME Record → Alias for subdomains
       |-- MX Record → Points to Mail Server
       |-- TXT Record → SPF, DKIM, Verification
       |-- Other Records (AAAA, SRV, etc.)
       |
       v
[DNS Resolver] (Queries the NS to get IPs)
       |
       v
[Hosting Server]      [Mail Server]
       |                    |
       v                    v
[Website Files]       [Email Delivery & Storage]

Explanation:

Domain Name: Your website address (e.g., example.com)

Nameserver (NS): Determines which DNS service manages the domain

DNS Records: Tell the world how to connect to your domain

  • A Record: Maps domain to server IP (for hosting)
  • CNAME: Alias or subdomain mapping
  • MX: Points to email server
  • TXT: SPF, DKIM, or verification records

DNS Resolver: The client-side or ISP-side resolver that queries nameservers to translate the domain into an IP address

Hosting Server: Stores your website files

Mail Server: Handles sending/receiving emails

💡 Key point: The DNS Resolver sits between the DNS Records and the Hosting/Mail Servers, because it’s what actually asks the nameserver for the IP to connect.

Example:

  1. You type a domain in your browser (e.g., example.com).
  2. The DNS Resolver (usually your ISP or a public resolver like Google DNS) receives this request.
  3. The resolver queries the Nameserver for the domain.
  4. The Nameserver responds with the appropriate DNS records (A, CNAME, MX, etc.).
  5. The resolver returns the IP address to your browser.
  6. Your browser then connects to the Hosting Server for the website or the Mail Server for email.

Domain

A domain is a human-readable address used to access websites on the internet. It maps to an IP address, which identifies the server hosting the website.

Example:

  • Domain: example.com
  • IP Address: 93.184.216.34

Parts of a Domain:

  • Top-Level Domain (TLD): .com, .org, .net
  • Second-Level Domain (SLD): example in example.com
  • Subdomain: Optional prefix like blog.example.com
  • Host: Specific machine or service within a domain. Often used interchangeably with subdomain in some contexts. Example: www in www.example.com.

Nameserver

A nameserver is a server responsible for translating domain names into IP addresses. It is part of the Domain Name System (DNS).

Types of Nameservers:

  1. Authoritative Nameserver:

    • Stores DNS records for a domain.
    • Provides definitive answers for DNS queries.

  2. Recursive Resolver (DNS Resolver):

    • Queries multiple nameservers to find the IP address for a domain.
    • Usually provided by ISPs or third-party services like Google DNS (8.8.8.8) or Cloudflare (1.1.1.1).

DNS Resolver vs Nameserver

While both DNS resolvers and nameservers are involved in translating domain names to IP addresses, they serve different roles:

Term Role Example / Notes
DNS Resolver (Recursive Resolver) Queries multiple nameservers on behalf of the client to find the IP address for a domain. Provided by ISPs or third-party services like Google DNS (8.8.8.8) or Cloudflare (1.1.1.1). It doesn’t store authoritative records, only caches results.
Nameserver Stores DNS records and provides authoritative answers for a domain. Authoritative nameservers like ns1.example.com contain the actual DNS records (A, MX, CNAME, etc.).

Key Differences:

  1. Purpose:

    • Resolver: Finds the IP for a domain.
    • Nameserver: Tells the resolver what the IP is.

  2. Authority:

    • Resolver: Not authoritative; relies on nameservers for correct answers.
    • Nameserver: Authoritative; stores and serves the definitive records for a domain.

  3. Interaction Flow:

    • Client → DNS Resolver → Nameserver(s) → Resolver → Client

Simplified Analogy:

  • Think of a DNS resolver as a librarian helping you find a book.
  • A nameserver is the actual bookshelf with the book on it.

DNS Records

DNS records are stored on authoritative nameservers and tell the internet how to route traffic for a domain.

Common DNS Record Types:

Record Type Purpose
A Maps a domain or host to an IPv4 address
AAAA Maps a domain or host to an IPv6 address
CNAME Maps a domain or subdomain to another domain (alias)
MX Directs email to mail servers
TXT Stores text information for verification or security (SPF, DKIM)
NS Specifies the authoritative nameservers for a domain
PTR Maps IP addresses back to domain names (reverse DNS)
SRV Specifies services for a domain (like VoIP or chat)

Other Concepts:

  • Host: Individual device or service within a domain, e.g., mail.example.com.
  • Zone File: A file on an authoritative nameserver containing all DNS records for a domain.

DNS Resolution Flow

When a user types a domain into a browser, DNS resolution occurs in multiple steps:

  1. Browser Cache Check: Browser looks for cached IP addresses.
  2. Operating System Cache Check: OS cache is checked if the browser doesn’t have it.
  3. Recursive Resolver Query: Sent to the DNS resolver (ISP or third-party).
  4. Root Nameserver Query: Resolver asks root nameserver to find TLD server.
  5. TLD Nameserver Query: Resolver asks the TLD server (e.g., .com) for authoritative nameserver.
  6. Authoritative Nameserver Query: Authoritative server provides the IP address for the domain or host.
  7. Response Returned: Resolver returns IP to browser, which connects to the website.

Summary

  • Domain: Human-readable website address.
  • Subdomain / Host: Subsection or service under a domain.
  • Nameserver: Translates domain names to IP addresses.
  • DNS Resolver: Queries nameservers to find the IP for a domain.
  • DNS Records: Instructions defining traffic routing.
  • Zone File: Storage of all DNS records for a domain.
  • Resolution Flow: Step-by-step process of converting domain names to IP addresses.