What Is DNS and Why Can It Stop Working?

DNS (Domain Name System) is a network protocol that translates domain names into IP addresses. If DNS is not working correctly, websites, email servers, or other online services may become inaccessible.

Common causes of DNS issues include:

• Incorrect DNS record configuration – Misconfigured A, CNAME, MX, or NS records.
• DNS server outage or overload – ISP DNS servers may be temporarily unavailable.
• Corrupt or outdated DNS cache – The system may be using outdated DNS records.
• Firewall or antivirus blocking DNS access – Some security software may interfere with DNS requests.

1. Verify the DNS Issue

Before attempting a fix, confirm that the issue is related to DNS.

nslookup example.com

If the IP address does not appear or you get an error "DNS request timed out", the problem is with DNS.

2. Clear the DNS Cache

Flushing the DNS cache can remove outdated or corrupt DNS records.

Windows:

ipconfig /flushdns

macOS:

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Linux:

sudo systemctl restart nscd

3. Restart the Modem and Router

Turn off your modem/router for 30 seconds and turn it back on. If using Wi-Fi, try connecting via cable to see if the problem persists.

4. Change DNS Server to a Public DNS

If your ISP’s DNS servers are unreliable, switch to faster and more stable alternatives.

• Google DNS: 8.8.8.8, 8.8.4.4
• Cloudflare DNS: 1.1.1.1, 1.0.0.1

5. Verify Proper DNS Routing

Use online tools to check current DNS records:

• DNS Checker – Checks DNS propagation worldwide.
• IntoDNS – Analyzes DNS configuration for a domain.

Check the route with traceroute:

Windows:

tracert example.com

Linux/macOS:

traceroute example.com

6. Check Firewall and Antivirus

Some security programs may block DNS queries. Temporarily disable your firewall or antivirus and test the connection.

Temporarily disable Windows firewall:

netsh advfirewall set allprofiles state off

Re-enable the firewall:

netsh advfirewall set allprofiles state on

7. Reset Network Settings

If none of the above solutions work, reset your network settings:

Windows:

netsh int ip reset
netsh winsock reset
ipconfig /release
ipconfig /renew
ipconfig /flushdns

Linux/macOS:

sudo systemctl restart NetworkManager

8. Contact Your Internet Service Provider (ISP)

If the issue persists, it may be caused by your ISP. Contact their technical support to check if their DNS servers are down.

Fixing DNS issues may require multiple steps, from clearing the cache to changing DNS servers. If you experience frequent DNS problems, consider using reliable public DNS or setting up a private DNS server. If the issue continues, reach out to your ISP for assistance.