DNS Learning Center
Learn how DNS works with easy-to-understand explanations and real-world examples
DNS Fundamentals
What is DNS?
The Domain Name System (DNS) is like the phonebook of the internet. It translates human-readable domain names (like google.com) into IP addresses (like 172.217.4.46) that computers use to communicate.
💡 Real-World Analogy
Think of DNS like a postal system: you write a name and address on an envelope, and the postal service knows exactly where to deliver it.
Key Points
- Translates domain names to IP addresses
- Distributed database system
- Essential for internet functionality
- Works behind the scenes automatically
How DNS Works
When you type a website address, your computer asks DNS servers to find the correct IP address. This happens through a series of queries to different types of DNS servers.
💡 Real-World Analogy
Like asking for directions: you ask a local guide, who might direct you to a regional expert, who then gives you the exact address.
Key Points
- Recursive queries start from your device
- Multiple DNS servers work together
- Caching speeds up subsequent requests
- Usually takes milliseconds to complete
DNS Hierarchy
DNS is organized in a tree-like structure, starting from the root domain at the top, then Top-Level Domains (TLDs), second-level domains, and subdomains.
💡 Real-World Analogy
Like a filing system: Root → Country → State → City → Street → House Number
Key Points
- Root domain (.) at the top
- TLDs like .com, .org, .net
- Second-level domains (google in google.com)
- Subdomains (www in www.google.com)
How DNS Resolution Works
Follow the journey of a DNS query from your browser to the final IP address in 7 simple steps
User Types Domain
You type a domain name like "example.com" in your browser
Your browser needs to find the IP address for this domain to establish a connection.
Check Local Cache
Your computer first checks if it already knows the IP address
Operating systems cache DNS responses to speed up repeated visits to the same sites.
Query DNS Resolver
If not cached, your computer asks your configured DNS resolver (ISP or public DNS)
This is usually configured automatically by your ISP or manually set to services like 8.8.8.8.
Root Server Query
DNS resolver asks root nameservers for TLD information
Root servers know which servers handle each top-level domain (.com, .org, etc.).
TLD Server Query
Resolver asks TLD servers which nameservers handle the domain
TLD servers (.com servers) know which nameservers are authoritative for example.com.
Authoritative Query
Resolver asks the authoritative nameserver for the IP address
The authoritative nameserver for example.com returns the actual IP address.
Return Response
The IP address is returned to your browser, which can now connect to the website
This response is cached at multiple levels to speed up future requests.
DNS Components Explained
DNS Servers
Recursive Resolver
Acts as an intermediary between clients and authoritative servers
Example: Your ISP's DNS server, Google DNS (8.8.8.8), Cloudflare (1.1.1.1)
Root Nameserver
Top-level servers that direct queries to TLD servers
Example: 13 root server clusters worldwide (a.root-servers.net to m.root-servers.net)
TLD Nameserver
Handles queries for specific top-level domains
Example: .com servers, .org servers, country code servers like .uk
Authoritative Nameserver
Contains the actual DNS records for a domain
Example: Your domain registrar's nameservers or your hosting provider's DNS
DNS Records
A Record
Maps domain to IPv4 address
Example: example.com → 192.0.2.1
AAAA Record
Maps domain to IPv6 address
Example: example.com → 2001:db8::1
CNAME Record
Creates an alias pointing to another domain
Example: www.example.com → example.com
MX Record
Specifies mail servers for the domain
Example: example.com → mail.example.com (priority 10)
Essential DNS Terminology
TTL (Time To Live)
How long DNS records should be cached before checking for updates
Example: TTL of 3600 means cache for 1 hour
DNS Propagation
Time it takes for DNS changes to spread across all DNS servers worldwide
Example: Can take 24-48 hours for complete global propagation
Nameserver
A server that stores DNS records and answers DNS queries
Example: ns1.example.com, ns2.example.com
Zone File
A text file containing DNS records for a particular domain
Example: Contains A, CNAME, MX records for a domain
FQDN (Fully Qualified Domain Name)
Complete domain name including all levels of the DNS hierarchy
Example: www.example.com. (note the trailing dot)
DNS Cache
Temporary storage of DNS query results to speed up future requests
Example: Your browser caches DNS lookups for recently visited sites
Try DNS Commands
Learn DNS by trying these commands in your terminal or command prompt
Basic DNS Lookup
See how a simple domain resolves to an IP address
$ nslookup google.comThis shows the A record (IPv4 address) for google.com
Detailed DNS Query
Get comprehensive information about a domain
$ dig google.com ANYShows all available DNS records for the domain
Reverse DNS Lookup
Find the domain name for an IP address
$ nslookup 8.8.8.8Shows what domain name points to this IP (PTR record)
Trace DNS Path
Follow the complete DNS resolution process
$ dig +trace google.comShows each step from root servers to final answer
DNS Hierarchy Visualization
DNS hierarchy flows from top to bottom. Each level knows which servers handle the next level down, creating a distributed system that can resolve any domain name on the internet.
Ready to Explore More?
Now that you understand DNS basics, try our tools and learn advanced concepts.