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Ridondanza, secondari e anycast
Redundancy, secondaries, and anycast
DNS redundancy helps a zone keep answering when a server or path fails. Several name-server names that all point to one machine do not provide real diversity. Servers on independent networks and providers are more resilient. Anycast announces the same IP address from multiple locations and lets routing choose a site, but routing failures can move or isolate traffic.
A hidden primary and public secondaries can separate administration from service; the primary does not necessarily need to appear in public NS records. Check that each secondary has current zone data, sites are genuinely independent, and the parent’s delegation matches the child’s NS records.
Four name servers across two providers may still share a failure mode if they use one compromised account or one management system. Consider network, provider, software, credential, and human failures. For a small zone, reliable secondaries may be a better choice than operating an anycast network without the needed expertise.
Reference: RFC 9199 — considerations for authoritative operators
Check your understanding
Choose the best answer. The examples use training names and do not send real DNS queries.
What makes name-server diversity meaningful?