When your domain name does not resolve to your server's IP address, visitors cannot reach your website. DNS issues can be caused by misconfigured records, propagation delays, or registrar problems. This guide helps you diagnose and fix the most common DNS resolution failures.

Diagnosing the Problem

Check if DNS Is Resolving

dig example.com A +short

• Shows your server IP — DNS is working. The issue may be elsewhere (web server, firewall).
• Shows the wrong IP — DNS records are pointing to an old or incorrect server.
• No output — DNS records are missing or not propagated.

Check with Multiple DNS Servers

# Google DNS
dig @8.8.8.8 example.com A +short
Cloudflare DNS
dig @1.1.1.1 example.com A +short
Your authoritative nameserver
dig @ns1.yourdns.com example.com A +short

If your authoritative nameserver returns the correct IP but public DNS does not, the issue is propagation.

Check Name Servers

dig example.com NS +short

Verify the name servers match what your domain registrar is configured to use.

Common Causes and Fixes

1. Missing A Record

Symptom: dig returns no result.

Fix: Add an A record at your DNS provider:

• Type: A
• Name: @ (for root domain) or subdomain name
• Value: Your server IP (e.g., 203.0.113.10)
• TTL: 3600

2. Wrong IP in A Record

Symptom: dig returns an IP that is not your server.

Fix: Update the A record with the correct Data Mammoth server IP. Find your IP in the server dashboard.

3. DNS Propagation Delay

Symptom: Changes made recently are not reflecting.

DNS changes can take up to 48 hours to propagate globally, though most update within 1 to 4 hours.

Fix:

• Wait for propagation to complete.
• Lower your TTL to 300 seconds (5 minutes) before making DNS changes to speed up future propagation.
• Use online propagation checker tools to monitor progress.

4. Wrong Name Servers

Symptom: Name servers at the registrar do not match your DNS provider.

Fix:

5. Expired Domain

Symptom: Domain returns NXDOMAIN or SERVFAIL.

Fix: Check your domain registration status at your registrar. Renew the domain if expired. Recently expired domains may enter a grace period where they can still be renewed.

6. CNAME on Root Domain

Symptom: Root domain does not resolve but subdomains work.

Fix: Some DNS providers do not support CNAME records on the root domain (@). Use an A record for the root domain instead. Some providers offer ALIAS or ANAME records that work like CNAME on the root.

7. Cached Old DNS

Symptom: Your computer shows old DNS but others see the correct IP.

Fix: Clear your local DNS cache:

# macOS
sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder
Linux
sudo systemd-resolve --flush-caches
Windows (Command Prompt)
ipconfig /flushdns

Also check your /etc/hosts file for manual overrides:

cat /etc/hosts

Remove any entries pointing your domain to an incorrect IP.

Verifying the Fix

After making changes:

# Check A record
dig example.com A +short
Check from a specific DNS server
dig @8.8.8.8 example.com A +short
Verify the web server responds
curl -I http://example.com

Prevention

What to Do Next

• Server Networking — IPs, DNS, Reverse DNS — Complete DNS configuration guide.
• Website Down — Quick Diagnosis Steps — If DNS is correct but site is still down.
• Email Not Sending from Server — DNS affects email too.
• SSL/TLS Certificates — SSL requires correct DNS.