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Questions: DNS Resolution Taking 5+ Seconds Intermittently

  • What DNS servers are configured in /etc/resolv.conf, and in what order?
  • Is the primary DNS server reachable (ping, dig @primary)?
  • What does dig with timing show when querying the primary vs. secondary server directly?
  • Does a packet capture show the DNS query being sent to the primary and timing out?
  • What is the options timeout and options attempts setting in resolv.conf?
  • Is the primary DNS server actually down, or is it reachable but dropping UDP 53?
  • Are there firewall rules between the hosts and the primary DNS server?
  • Has the primary DNS server's IP address changed or been decommissioned recently?
  • Does the issue correlate with specific times of day or load patterns?
  • Are there any network path changes that could cause the primary to be intermittently unreachable?