DNS Issues

Nameserver Not Responding

When a nameserver stops responding, DNS resolution fails for all domains it hosts. This causes websites to become unreachable and email delivery to stop. Nameserver issues can stem from server outages, DDoS attacks, misconfigured firewall rules, or expired nameserver domain registrations.

Symptoms

  • All domains on the nameserver become unreachable
  • DNS queries time out with SERVFAIL responses
  • nslookup or dig commands return "connection timed out"
  • Intermittent resolution failures if only one of multiple NS records is down

Common Causes

  • Nameserver host experiencing an outage
  • DDoS attack targeting the nameserver
  • Firewall blocking DNS traffic (port 53 UDP/TCP)
  • Nameserver domain registration expired
  • Misconfigured glue records at the registrar

Step-by-Step Troubleshooting

  1. 1

    Check NS records

    Verify which nameservers are configured for the domain and confirm they are correct.

    Use NS Record Lookup →
  2. 2

    Test nameserver connectivity

    Use ping or traceroute to check if the nameserver IP is reachable.

    Use Ping & Traceroute →
  3. 3

    Check port 53 availability

    Verify that DNS port 53 is open on the nameserver.

    Use Port Scanner →
  4. 4

    Verify WHOIS nameserver delegation

    Confirm the registrar has the correct nameserver delegation.

    Use WHOIS Lookup →

Recommended Diagnostic Tools

NS Record LookupPing & TraceroutePort Scanner

Monitor Nameserver Uptime

Track nameserver availability and get alerts on DNS failures.

Related Problems

Frequently Asked Questions