Isolating the Failure
DNS issues manifest as "Server Not Found" errors. The first step is isolating whether the problem is on the local client, the resolver, the registrar, or the authoritative server.
Diagnostic Tools (dig and nslookup)
Use the terminal command `dig` to perform direct lookups. Query specific servers directly to bypass local resolver caching and see raw nameserver responses.
BASH Snippet
bash
# Query Google DNS for an A record
dig @8.8.8.8 example.com A
# Trace the nameserver tree step-by-step
dig example.com +traceCommon DNS Errors
- NXDOMAIN: The domain name does not exist. Check spelling and registrar activation.
- SERVFAIL: The recursive resolver was unable to retrieve a response. This often points to nameserver configuration errors or expired DNSSEC keys.
- REFUSED: The nameserver refused to answer, often due to access controls or rate limits.