What is a DNS Server?

A DNS server (Domain Name System server) is the backbone of the Internet's address book. It translates easy-to-remember domain names—like example.com—into numerical IP addresses such as 93.184.216.34. Without DNS servers, every online action—from opening websites to sending emails—would require typing IP addresses manually.

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Why DNS Servers Exist

People use domain names, machines use IP addresses.

The DNS server bridges this gap, enabling smooth communication between browsers and servers.

Defined in IETF RFC 1034 and RFC 1035, DNS is a distributed, hierarchical system ensuring redundancy and reliability across the global internet infrastructure.

Key Entities: Domain Name System, ICANN, IANA, IP addressing (IPv4/IPv6), network resolution, root name server.

How a DNS Server Works (Step by Step)

Understanding the DNS resolution process is fundamental to grasping how the internet works:

1

User Types Domain

User types www.example.com in a browser.

2

Request to Recursive Resolver

The request goes to a recursive DNS resolver (often your ISP or public DNS like Google DNS 8.8.8.8 or Cloudflare 1.1.1.1).

3

Query Root Server

The resolver asks a root server which TLD to contact. There are 13 root server systems managed by organizations like ICANN and Verisign.

4

Root Directs to TLD

The root directs it to the correct TLD server (like .com, .org, or .net).

5

TLD Points to Authoritative Server

The TLD points to the authoritative server for example.com.

6

Authoritative Server Returns IP

The authoritative server returns the IP address to the browser.

7

Browser Connects

The browser connects and loads the website.

Verify this live using our DNS Lookup Tool.

Types of DNS Servers

Type Description Example
Recursive Resolver Receives user queries, looks up and caches answers. Google 8.8.8.8 / Cloudflare 1.1.1.1
Root Name Server Top-level directory for all TLDs. a.root-servers.net
TLD Server Stores info for .com, .org, .net, etc. Managed by Verisign, PIR
Authoritative Name Server Holds actual DNS records (A, MX, NS, TXT). ns1.example.com

DNS Record Types Managed by Servers

DNS servers manage various record types to route traffic correctly:

  • A — Maps domain to IPv4 address
  • AAAA — Maps domain to IPv6 address
  • CNAME — Canonical name / alias
  • MX — Mail exchange servers
  • NS — Name servers for the zone
  • SOA — Start of Authority (zone metadata)
  • TXT — Text data (SPF, DKIM, verification)
  • PTR — Reverse DNS (IP → domain)
  • SRV — Service locator
  • CAA — Certificate Authority Authorization

For a comprehensive guide, check our What is DNS article.

DNS Server Protocols and Ports

Standard DNS

  • UDP 53 — Default query transport (fast, lightweight)
  • TCP 53 — Large or zone-transfer traffic

Encrypted DNS Protocols

  • DoH (DNS over HTTPS) — Encrypts DNS queries using HTTPS. Defined in RFC 8484.
  • DoT (DNS over TLS) — Encrypts DNS using TLS 1.3 on port 853.

Entities: RFC 8484, TLS 1.3, HTTPS GET/POST, IETF

DNS Server Security Features

DNSSEC

DNSSEC prevents spoofing with cryptographic signatures using RRSIG, DNSKEY, and DS records.

It creates a chain of trust from the root zone to individual domains, ensuring DNS responses are authentic and unmodified.

Anycast Networks

Distribute load globally using the same IP addresses at multiple locations. Used by Cloudflare and Verisign to improve reliability and reduce latency.

Rate-Limiting & Query Validation

Block DDoS and cache poisoning attacks through intelligent query filtering and response rate limiting.

DNS Caching & TTL

Cached responses improve speed. DNS resolvers and browsers cache query results to reduce latency and server load.

TTL (Time To Live)

TTL controls cache duration:

  • TTL = 3600 → 1 hour caching
  • TTL = 300 → 5 minutes caching
  • TTL = 86400 → 24 hours caching

Clearing DNS Cache

Windows: ipconfig /flushdns
macOS: sudo dscacheutil -flushcache
Linux: sudo systemd-resolve --flush-caches

How to Run Your Own DNS Server

Running your own DNS server gives full control over your zones, privacy, and performance. You can set up one for internal use (LAN, VPN, intranet) or for public hosting.

Requirements

  • Server: Linux (Ubuntu 24.04 LTS or Debian 12 recommended)
  • Static IP address
  • Domain name (if authoritative)
  • Firewall open on UDP/TCP 53

Example Setup Using BIND 9

1. Install BIND

sudo apt update

sudo apt install bind9 bind9utils bind9-doc

2. Configure Zone File

Edit /etc/bind/named.conf.local

zone "example.com" {

    type master;

    file "/etc/bind/zones/db.example.com";

};

3. Create Zone Data File

Create /etc/bind/zones/db.example.com

$TTL 3600

@ IN SOA ns1.example.com. admin.example.com. (

    2025102401 ; Serial

    3600 ; Refresh

    1800 ; Retry

    604800 ; Expire

    86400 ) ; Minimum TTL

@ IN NS ns1.example.com.

ns1 IN A 192.0.2.10

@ IN A 192.0.2.20

www IN A 192.0.2.21

4. Restart Service

sudo systemctl restart bind9

sudo systemctl enable bind9

5. Verify

dig @127.0.0.1 example.com A

✅ You now have an authoritative DNS server running locally.

Running a Recursive DNS Resolver (Unbound)

1. Install Unbound

sudo apt install unbound

2. Edit Configuration

Edit /etc/unbound/unbound.conf

server:

    interface: 0.0.0.0

    access-control: 0.0.0.0/0 allow

    verbosity: 1

    hide-identity: yes

    hide-version: yes

3. Restart and Test

sudo systemctl restart unbound

dig @127.0.0.1 google.com

✅ You now have a recursive resolver caching queries for faster performance.

Popular Open-Source DNS Server Software

Software Type Description Homepage
BIND 9 Authoritative / Recursive Most widely used, maintained by ISC, supports DNSSEC. isc.org/bind
PowerDNS Authoritative + Recursor High-performance, database-backed, API integration. powerdns.com
Unbound Recursive Lightweight, secure caching resolver (NLnet Labs). nlnetlabs.nl
Knot DNS Authoritative Modern high-speed DNS server from CZ.NIC. knot-dns.cz
MaraDNS Authoritative / Recursive Simple, small footprint for embedded use. maradns.samiam.org
NSD Authoritative Compact, DNSSEC-enabled authoritative server. nlnetlabs.nl
CoreDNS Cloud-native DNS server built in Go, used by Kubernetes clusters. coredns.io

Key Entities: BIND, Unbound, PowerDNS, CoreDNS, Knot DNS, MaraDNS, NSD, ISC, NLnet Labs.

When to Run Your Own DNS Server

Running your own DNS server makes sense in these scenarios:

You manage many domains or internal subdomains

Complete control over DNS zones and records

You need fast response times for a closed network

Internal DNS for LAN, VPN, or private networks

You want privacy

No external resolver logging your DNS queries

You develop network monitoring, VPN, or custom ISP tools

Full control and customization for specialized use cases

Frequently Asked Questions

1. What does a DNS server actually do?

It translates domain names into IP addresses and routes requests to the correct server. Without DNS servers, you would need to memorize numerical IP addresses for every website you visit.

2. Is it safe to run my own DNS server?

Yes—if properly firewalled and updated. Always restrict zone transfers and enable DNSSEC if public. Implement security best practices including rate-limiting, access controls, and regular software updates.

3. What's the best open-source DNS software?

BIND for flexibility, Unbound for simplicity, PowerDNS for database and API integration, CoreDNS for containers. The best choice depends on your specific requirements and infrastructure.

4. How can I test my DNS server?

Use dig @your-server-ip domain.com or web tools like DNS Lookup.

5. Can I combine authoritative and recursive servers?

Yes, but separate them for security and performance best practices. Authoritative servers should only serve your own zones, while recursive resolvers should only serve trusted clients. Mixing both on the same server can create security vulnerabilities.

Test Your DNS Server Setup

Want to verify your DNS configuration? Use our free DNS Lookup Tool to check DNS records and ensure everything is working correctly.

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