Decoding Error Codes
NXDOMAIN
Non-Existent Domain
The domain does not exist. Check for typos or verify the domain is registered and active at your registrar.
SERVFAIL
Server Failure
The resolver was unable to get an answer. Often caused by DNSSEC validation failures or dead authoritative nameservers.
REFUSED
The nameserver refused to perform the query, often due to policy restrictions (e.g., trying to use an authoritative server as a recursive resolver).
NOERROR (Empty Answer)
The domain exists, but the specific record type you requested (e.g., AAAA) does not exist for that name.
Mastering the `dig` Command
The Domain Information Groper (`dig`) is the gold standard for DNS troubleshooting.
# Basic lookup
dig example.com
# Query a specific nameserver (bypass cache)
dig @1.1.1.1 example.com
# Trace the delegation path from the root
dig example.com +trace
# Short answer only
dig example.com +short
Propagation Myths
DNS doesn't "propagate" in a linear fashion. It's all about TTL (Time to Live).
When you change a record, resolvers that have the old record cached will wait until the TTL expires before fetching the new one.
Pro Tip: Lower your TTL to 300 seconds (5 minutes) 24 hours before making a planned change.
Flushing Your Cache
macOS:
sudo killall -HUP mDNSResponder
Windows:
ipconfig /flushdns
Chrome:
chrome://net-internals/#dns