Abhay Dixit

Full Stack Developer

Understanding How DNS Works: Resolving Domain Names to IP Addresses

When you type abhaydixit.hashnode.dev into your browser, the browser doesn’t inherently know where the website is hosted. Instead, it uses the Domain Name System (DNS) to find the corresponding IP address. DNS is essentially a database of key-value pairs that map domain names to IP addresses.

List of Common DNS Servers

DNS servers help resolve domain names into IP addresses. Here are some well-known DNS servers:

  • Cloudflare → 1.1.1.1
  • Google → 8.8.8.8

Your computer is configured to use a specific DNS server, which determines where DNS queries are sent.

The DNS Resolution Process

1. Request to the Root Server

When a DNS query is made, the request is first sent to a root server. There are 13 root servers worldwide, and their details can be checked at root-servers.org.

2. Top-Level Domain (TLD) Server

The root server determines the Top-Level Domain (TLD), such as .com, .dev, .org, .edu, and returns the corresponding IP address for the TLD’s root servers.

3. Query to the Authoritative Server

The request is then sent to the authoritative DNS server, which is typically managed by hosting providers like Google, GoDaddy, or Cloudflare. This server holds the actual IP address for the requested domain.

Understanding DNS Records

DNS records store information about a domain and its associated resources. Some common types include:

  • A Record → Maps a domain name to an IPv4 address (e.g., 192.168.1.1).
  • CNAME Record → Used to alias one domain name to another (e.g., www.example.com to example.com).
  • NS Record → Specifies the authoritative name servers for a domain.

Example:

  • @ → Represents hashnode.dev.
  • tutorial → Represents tutorial.hashnode.dev.
  • A Record → The simplest DNS record type, mapping a domain name to an IP address.
  • CNAME Record → Used for pointing subdomains to another domain.
  • NS Record → Specifies the authoritative name server, which itself contains an A Record mapping it to an IP.

Difference Between NS Record and A Record

  • NS Record → Points to a name server.
  • A Record → Provides the actual IP address.

Example:

abhaydixit.hashnode.dev NS ns.hostinger.com

This sets ns.hostinger.com as the authoritative name server for abhaydixit.hashnode.dev.

DNS and Networking Tools

DNS primarily works over the UDP protocol on port 53, which is a connectionless protocol.

Checking Network Interfaces

  • ifconfig → Lists all network interfaces (deprecated on some Linux versions).
  • ip addr show → Alternative to ifconfig.

Editing the Hosts File

To manually map IP addresses to hostnames, modify the hosts file:

sudo vi /etc/hosts

Add an entry in the following format:

192.168.1.100 mypc.local

Now, mypc.local can be used in networking commands.

Checking Open Ports and Processes

  • netstat -antp → Displays a list of all open ports.
  • ss -tnlp → Shows process IDs and listening ports.
  • nmap localhost → Scans for open ports on localhost.

DNS Query Testing

  • dig www.google.com → Checks if the DNS resolution works from your computer.
  • dig @localhost www.google.com → Uses the localhost’s DNS resolver.

Conclusion

DNS is an essential system that translates domain names into IP addresses, enabling seamless web browsing. Understanding how DNS queries work and how to troubleshoot them using networking commands can be crucial for developers and network administrators alike.