Grading Checklist: DNS Resolution Taking 5+ Seconds Intermittently

• Examined /etc/resolv.conf to identify primary and secondary nameservers
• Tested DNS resolution against each nameserver individually using dig @<server>
• Identified that the primary DNS server is unreachable or dropping queries
• Explained the resolver fallback mechanism (timeout on primary, then try secondary)
• Noted that the ~5 second delay matches the default resolver timeout
• Used tcpdump/packet capture to show the timeout on the first query
• Proposed immediate fix: swap nameserver order or remove the dead primary
• Proposed long-term fix: investigate and restore the primary DNS server
• Mentioned resolv.conf options (timeout, attempts, rotate) and their effects
• Discussed impact on applications with short connection timeouts
• Considered using a local caching resolver (systemd-resolved, dnsmasq) to minimize impact
• Verified the fix by running timed DNS queries after the change