Why Is DNS Resolution Failing?
DNS resolution failures return specific RCODE values that indicate different categories of problems. This decision tree helps you diagnose whether the issue is connectivity, domain registration, nameserver configuration, or a server-side processing error.
Decision Steps
Can you reach any DNS resolver at all (e.g., does 'dig @8.8.8.8 google.com' work)?
Is the domain registered and has it not expired (check WHOIS)?
Are the authoritative nameservers for the domain responding (e.g., 'dig NS yourdomain.com' returns records)?
Does the DNS record you are querying (A, AAAA, CNAME, etc.) actually exist on the nameserver?
Is the DNS query itself malformed (e.g., invalid class, unsupported opcode, corrupt packet)?
Is the resolver refusing to answer queries for this zone (access control or policy)?