Troubleshooting DNS Issues

DNS problems can be frustrating and hard to track down. Here are some practical steps and tools to diagnose what’s going wrong.

Quick Diagnostic Commands

Check Your DNS Configuration

First, verify which DNS servers your system is using:

# Linux/Mac
cat /etc/resolv.conf

# Windows
ipconfig /all

Test DNS Resolution

Use nslookup or dig to query DNS directly:

# Simple lookup
nslookup google.com

# Detailed response with dig
dig google.com

# Specify a particular DNS server
dig @8.8.8.8 google.com

Common Issues & Solutions

DNS Not Resolving

If names aren’t resolving to IPs:

• Check connectivity first — can you ping the DNS server itself?
• Try a different DNS server — test with 8.8.8.8 or 1.1.1.1
• Flush DNS cache — sudo systemctl restart systemd-resolved (Linux) or ipconfig /flushdns (Windows)

Slow DNS Queries

If resolution is sluggish:

• Check for timeouts — use dig +stats to see query time
• Too many hops — consider switching to a faster DNS provider
• Local DNS cache issues — restart your DNS service

NXDOMAIN Errors

This means the domain doesn’t exist in DNS:

• Verify the domain name — typos are common
• Check DNS propagation — new domains take time to propagate
• Try another DNS server — sometimes specific providers don’t have updated records

Tools That Help

• dig — most detailed DNS lookups
• nslookup — simpler alternative to dig
• host — quick hostname resolution
• dnstracer — trace the DNS resolution path
• whois — check domain registration info

Prevention

Configure multiple DNS servers for redundancy, and consider using a local DNS cache like Pi-hole to reduce resolution time and add a layer of control.