Introduction to DNS
What is DNS ?
DNS stand for Domain Name Server , it convert domain name to ip address . For example gokuthecoder.me to “192.0.4.56” . It is generally called phone contact for the internet , just instead of remember number just put domain name on browser it redirect on that ip address .
The Role of DNS in the Internet Ecosystem
DNS is the core foundation component of the imternet Ecosystem, that translate human readable name google.com into machine reable ip address 142.251.42.206
Why DNS is Critical for Websites and Applications
DNS is like a Internet GPS. it make web and apps work smooth , below is key points
Translate names into IP : it turn change name like google.com to 142.251.42.206
Keep thing easy : If server has been crashes it redirect traffic to backup server
Speed up: in video streaming and payment site direct user to closest server
Email work: If you send email then dns ensure that email send to right server like , if i send mail to example.google.com then dns ensure that email reach on gmail server through MX (Mail Exchange Record)
How DNS Works
The DNS Query Process : Step-by-Step
DNS query works when you write domain on Browser example.com .
User Initiate a Request
You type example.com
Browser first check domain in local cache is it know ip address for
example.comif know then skip all rest of step
Query the Recursive Resolver
If the browser doesn’t have the IP cached then it ask to DNS recursive resolver (usully provide by your ISP or third party like Google DNS or Cloudflare)
The Resolver check its own cache . if cached , it return then ip address IP address immedietly
Root Server Query
If the resolve has no cache record , it start DNS lookup process:
First it contacts of the 13 roor DNS (these all 13 root server which manage by ICANN ).
ICANN (Internet Corporation for Assigned Names and Numbers).
List of Root Servers
198.41.0.4, 2001:503:ba3e::2:30
Verisign, Inc.
170.247.170.2, 2801:1b8:10::b
University of Southern California,
Information Sciences Institute192.33.4.12, 2001:500:2::c
Cogent Communications
199.7.91.13, 2001:500:2d::d
University of Maryland
192.203.230.10, 2001:500:a8::e
NASA (Ames Research Center)
192.5.5.241, 2001:500:2f::f
Internet Systems Consortium, Inc.
192.112.36.4, 2001:500:12::d0d
US Department of Defense (NIC)
198.97.190.53, 2001:500:1::53
US Army (Research Lab)
192.36.148.17, 2001:7fe::53
Netnod
192.58.128.30, 2001:503:c27::2:30
Verisign, Inc.
193.0.14.129, 2001:7fd::1
RIPE NCC
199.7.83.42, 2001:500:9f::42
ICANN
202.12.27.33, 2001:dc3::35
WIDE Project
The roor server doed not know the ip of domain
example.com, but it directs the resolver to that authoritative name server forexample.com.
TLD Server Query
The resolver ask the .com TLD server (e.g., Verisign for
.comdomains).TLD does not store IP either but points the resolver to the authoritative name server for
example.com
Authoritative Name Server Query
The resolver contact the authoritative name server (manage by hosting domain’s hosting provider)
This server actually Hold the Actual DNS record (like A or AAAA record ) and return the IP address for example
Response to User
The resolver caches the ip address (for future requests) and send back to the browser.
your browser connect to the IP address , and the website loads .
Caching for Effeciency
- Every start (browser , OS, resolver) cache the IP for a set time (TTL / Time-to-Live) to speed up future request
Key Components of the DNS Infrastructure
The DNS (Domain Name Server) has several key componensts, including DNS resolvers, DNS servers, and DNS client.
DNS resolver
Receive DNS query from Client
Cache the response to speed up future
forward query to the another DNS server if the answer idn’t in the cache
DNS servers
ROOT DNS Server : The highest level DNS server that directs to the relevant TLD servers.
TOP-level domain (TLD) servers: Handle the last part of a domain name , like .com, .net, .org …etc.
DNS client
Software component that runs or initiates on the user device or application
Initiate DNS queries by sending them to DNS resolver
1. Important DNS Records
CNAME Record (Canonical Name Record)
It maps one domain name to another.
Example:blog.example.com→example.comA Record (Address Record)
A is stand for “address” this is most fundamental types of record : it used to point a domain or subdomain to an IPv4 address.
MX Record (Mail Exchange Record)
It tells where emails should go.
Example:example.com→mail.google.comTXT Record (Text Record)
Stores extra information, like email verification (SPF, DKIM).
Example: Used to verify domains in Google or Microsoft.NS Record (Name Server Record)
Points to the server managing the domain.
Example:example.com→ns1.provider.comAAAA Record (IPv6 Address Record)
Connects a domain to an IPv6 address (newer internet protocol).
Example:example.com→2001:db8::ff00:42:8329
2. Common DNS Issues and How to Fix Them
DNS Propagation Delays
When you change DNS settings, it takes time (few hours to 48 hours) to update worldwide.
Fix: Wait or clear your DNS cache.
DNS Cache Poisoning (Security Risk)
Attackers change DNS records to redirect users to fake websites.
Fix: Use secure DNS servers & enable DNSSEC.
DNS Resolution Errors
Happens when a domain can’t be found.
Fix:
Check your internet connection.
Flush DNS cache (
ipconfig /flushdnsin Windows).Use Google DNS (8.8.8.8, 8.8.4.4).
3. How to Use DNS Tools
dig (Linux & Mac users)
Check DNS records.
Example:
digexample.com
nslookup (Windows users)
Find IP of a domain.
Example:
nslookupexample.com