In Part 1, we learned:
- What DNS is
- Why DNS exists
- How DNS connects humans and computers
In Part 2, we explored:
- DNS hierarchy
- Root, TLD, and authoritative servers
- Step-by-step DNS resolution
- DNS caching and TTL
Now, in Part 3, we move into practical and real-world DNS knowledge.
This part will help you:
- Understand DNS records clearly
- Avoid common DNS mistakes
- Manage domains confidently
- Build awareness about DNS security
By the end, you will have a complete DNS foundation.
What Are DNS Records?
DNS records are instructions stored inside authoritative DNS servers.
They tell the internet:
- Where your website lives
- Where emails should be delivered
- How domain verification works
- Which servers control your domain
Each record has:
- A type
- A value
- A TTL (Time To Live)
Most Important DNS Record Types
1. A Record (Address Record)
Maps a domain name to an IPv4 address.
Example:
example.com → 93.184.216.34
Use case:
- Website hosting
- API endpoints
- Server access
This is the most basic and essential DNS record.
2. AAAA Record (IPv6 Address)
Maps a domain name to an IPv6 address.
Example:
example.com → 2001:db8::1
Used when:
- IPv6 networking is enabled
- Modern cloud infrastructure is used
3. CNAME Record (Canonical Name)
Creates an alias for another domain.
Example:
www.example.com → example.com
Important rules:
- CNAME cannot coexist with A records on the same name
- Used heavily in CDN and cloud services
4. MX Record (Mail Exchange)
Controls email delivery for a domain.
Example:
example.com → mail.example.com
MX records include priority numbers:
- Lower number = higher priority
Without correct MX records:
- Emails will not work
5. TXT Record (Text Record)
Stores verification and policy data.
Used for:
- Google site verification
- SPF (email security)
- DKIM
- Domain ownership proof
- AdSense validation
Example:
v=spf1 include:_spf.google.com ~all
TXT records are extremely important for email security.
6. NS Record (Nameserver Record)
Specifies which DNS servers control your domain.
Example:
ns1.cloudflare.com
ns2.cloudflare.com
Whoever controls the NS records:
Controls your domain’s DNS completely
7. SOA Record (Start of Authority)
Contains administrative information about the DNS zone.
Includes:
- Primary nameserver
- Admin email
- Serial number
- Refresh and retry timers
SOA record is automatically managed by DNS providers.
What Are Nameservers and Why They Matter
Nameservers are the authoritative source of truth for a domain.
When you change nameservers:
- All DNS control moves to the new provider
- Old DNS records stop working
- New records must be recreated
Important fact:
Changing nameservers does NOT change domain ownership or hosting.
It only changes who answers DNS queries.
DNS Propagation Explained Simply
DNS propagation is the time taken for DNS changes to update across the internet.
Why it happens:
- DNS data is cached globally
- Each cache expires based on TTL
Typical propagation time:
- Record updates: minutes to hours
- Nameserver changes: up to 24–48 hours
During propagation:
- Some users see old data
- Some see new data
This behavior is normal.
What Is DNS TTL?
TTL = Time To Live
It defines:
How long a DNS record is cached before rechecking.
Example:
TTL = 300 seconds
Meaning:
- Cache record for 5 minutes
- After that, refresh it
Lower TTL:
- Faster updates
- More DNS queries
Higher TTL:
- Better performance
- Slower changes
DNS Security Basics (Awareness Level)
DNS was not originally designed with security in mind.
Common DNS Risks:
- DNS spoofing
- Cache poisoning
- Traffic redirection
- Fake websites
DNSSEC (Brief Awareness)
DNSSEC adds:
- Cryptographic signatures
- Verification of DNS authenticity
- Protection against tampering
Not mandatory for all sites, but recommended for serious projects.
Common DNS Mistakes to Avoid
1. Deleting Records Blindly
Always understand before removing any DNS record.
2. Forgetting MX Records
This breaks email completely.
3. Incorrect CNAME Usage
CNAME at root domain can cause issues.
4. High TTL During Migration
Makes DNS changes slow.
5. Nameserver Change Without Backup
Can cause full website downtime.
DNS Best Practices
- Always keep at least 2 nameservers
- Use reliable DNS providers
- Keep TTL low during migrations
- Document DNS changes
- Regularly review DNS records
- Secure email with SPF, DKIM, and DMARC
- Avoid unnecessary records
Why DNS Knowledge Is a Power Skill
Understanding DNS helps you:
- Debug website issues
- Fix email problems
- Improve performance
- Avoid downtime
- Communicate better with hosting providers
- Grow as a developer or DevOps engineer
DNS is not just networking — it is internet literacy.
Final Summary of the DNS Series
Across all three parts, you learned:
- What DNS is and why it exists
- How DNS works internally
- DNS hierarchy and resolution flow
- DNS records and their purpose
- Nameservers and domain control
- DNS propagation and TTL
- DNS security awareness
- Best practices and common mistakes
You now have a complete, end-to-end understanding of DNS from scratch.
Next Steps :
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