Every time you type a website address into your browser, DNS (Domain Name System) silently translates that human-readable name into an IP address your computer can use to connect. Without DNS you would need to memorise a string of numbers for every website you visit. This guide explains how DNS works, the different types of DNS records and how to configure DNS in Windows environments.
What is DNS?
DNS is the internet’s address book — a distributed global database that maps domain names (like techygeekshome.info) to IP addresses (like 185.230.63.107). When you type a URL in your browser, your computer queries DNS servers to find the IP address associated with that domain, then connects to that IP address to load the website.
How a DNS Query Works — Step by Step
- Browser cache — your browser first checks its own cache to see if it recently resolved this domain
- Operating system cache — if not in the browser cache, Windows checks its local DNS cache
- Recursive resolver — if not cached locally, the query goes to your ISP’s or configured DNS server (e.g. Google 8.8.8.8)
- Root nameservers — the recursive resolver queries one of the 13 root nameservers to find which nameserver is responsible for the top-level domain (.com, .info, .uk etc)
- TLD nameserver — the root server refers the query to the TLD nameserver for .info
- Authoritative nameserver — the TLD server refers to the domain’s authoritative nameserver (e.g. Cloudflare’s nameservers for techygeekshome.info)
- DNS response — the authoritative server returns the IP address
- Connection — your browser connects to the returned IP address
This entire process typically completes in under 100 milliseconds.
Common DNS Record Types
| Record Type | Purpose | Example |
|---|---|---|
| A | Maps a domain to an IPv4 address | techygeekshome.info → 185.230.63.107 |
| AAAA | Maps a domain to an IPv6 address | techygeekshome.info → 2606:4700::1 |
| CNAME | Alias — points one domain to another | www.techygeekshome.info → techygeekshome.info |
| MX | Mail server for the domain | techygeekshome.info → mail.techygeekshome.info |
| TXT | Text data — used for SPF, DKIM, verification | v=spf1 include:spf.protection.outlook.com |
| NS | Nameservers for the domain | ns1.cloudflare.com |
| PTR | Reverse DNS — maps IP to hostname | 107.63.230.185.in-addr.arpa → techygeekshome.info |
| SRV | Service location records | Used by Active Directory, SIP, XMPP |
| SOA | Start of Authority — zone metadata | Primary nameserver and zone serial number |
DNS in Windows Environments
In Active Directory environments, DNS is critical infrastructure. Domain controllers run the Windows DNS Server role and host the DNS zones for your Active Directory domain. All domain-joined computers use the domain controller as their primary DNS server to resolve internal names.
Useful DNS Commands in Windows
# Check DNS resolution for a domain
nslookup techygeekshome.info
# Check which DNS server you are using
nslookup
# Flush the local DNS cache
ipconfig /flushdns
# Display the local DNS cache
ipconfig /displaydns
# Register the computer in DNS
ipconfig /registerdns
# Test DNS resolution with PowerShell
Resolve-DnsName techygeekshome.info
# Query a specific DNS server
Resolve-DnsName techygeekshome.info -Server 8.8.8.8Public DNS Servers Worth Knowing
| Provider | Primary DNS | Secondary DNS | Features |
|---|---|---|---|
| 8.8.8.8 | 8.8.4.4 | Fast, reliable, global | |
| Cloudflare | 1.1.1.1 | 1.0.0.1 | Fastest globally, privacy focused |
| OpenDNS | 208.67.222.222 | 208.67.220.220 | Content filtering options |
| AdGuard DNS | 94.140.14.14 | 94.140.15.15 | Ad blocking at DNS level |
| Quad9 | 9.9.9.9 | 149.112.112.112 | Security focused, blocks malware domains |
Frequently Asked Questions
What happens if DNS goes down?
If your DNS server is unreachable, you cannot resolve domain names — effectively meaning the internet stops working even though your network connection is fine. You can still reach websites by typing their IP address directly. This is why redundant DNS servers are critical in enterprise environments.
What is DNS TTL and why does it matter?
TTL (Time To Live) is a value on each DNS record that tells resolvers how long to cache the record before querying again. A low TTL (e.g. 300 seconds) means changes propagate quickly but generates more DNS queries. A high TTL (e.g. 86400 seconds) reduces queries but means changes take longer to propagate globally. When making DNS changes, lower the TTL 24-48 hours before the change for faster propagation.
What is the difference between internal and external DNS?
Internal DNS resolves names within your private network — hostnames of servers, printers and Active Directory resources. External DNS resolves public internet domains. In enterprise environments, internal DNS servers forward queries they cannot resolve to external DNS servers (forwarders), giving you both internal name resolution and internet access.
How do I change DNS servers in Windows?
Go to Settings → Network and Internet → select your connection → DNS server assignment → Edit → Manual → enter your preferred DNS server addresses. Alternatively via Control Panel → Network Connections → right-click your adapter → Properties → Internet Protocol Version 4 → Properties → enter DNS server addresses.
What is split-brain DNS?
Split-brain DNS (also called split-horizon DNS) uses the same domain name for both internal and external DNS but returns different IP addresses depending on whether the query comes from inside or outside your network. For example, mail.company.com resolves to a private IP internally but a public IP externally. This is common in Exchange and web server configurations.
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