Place authoritative DNS secondaries across independent failure domains

Keep this document to one review outcome: Place authoritative DNS secondaries across independent failure domains. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official RFC 2182 — Selection and Operation of Secondary DNS Servers from RFC Editor / Internet Engineering Task Force supports the following bounded statements:

• Authoritative secondary servers must be geographically dispersed and connected through diverse network paths so one failure cannot isolate all servers. The research record locates this support at Section 3.1 (Selecting Secondary Servers).
• Placing every authoritative server on one LAN, in one room, or in one building defeats most of the resilience gained from multiple servers. The research record locates this support at Section 3.2 (Unsuitable Configurations).
• Most organization-level zones should have three servers, with at least one well removed from the others; higher-reliability zones may use four or five. The research record locates this support at Section 5 (How many secondaries?).

These statements are the factual basis for this document. Do not extend them into a broader assurance. Review authoritative zones, delegations, resolvers, caches, record owners, and the clients that consume the resulting answers only where the source and recorded environment align.

What the source does not establish

This RFC evidence supports only the named DNS protocol decision; it does not prove Windows implementation support or a safe production configuration. No current deployment state or change approval follows from the source alone. Validate Windows DNS roles, Active Directory-integrated data, forwarding paths, time, routing, firewalls, and registrar or registry state, and treat examples or options as conditional inputs rather than defaults.

Applicability questions

• For source statement 1 at Section 3.1 (Selecting Secondary Servers), which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Section 3.2 (Unsuitable Configurations), which observable configuration, record, or test can confirm applicability here?
• For source statement 3 at Section 5 (How many secondaries?), which observable configuration, record, or test can confirm applicability here?
• Within authoritative zones, delegations, resolvers, caches, record owners, and the clients that consume the resulting answers, which versions, roles, and configuration states define the review population?
• Could Windows DNS roles, Active Directory-integrated data, forwarding paths, time, routing, firewalls, and registrar or registry state invalidate the test, hide a failure, or change applicability?
• Who owns the decision, and which observation requires stopping, escalation, or rollback?

DSE recommendation:

DSE recommends using the cited source as the evidence anchor for this decision. Start with applicability, then compare the observed state with the cited source. Record the source location, examined part of authoritative zones, delegations, resolvers, caches, record owners, and the clients that consume the resulting answers, observed and expected states, owner, and reason for deviation.

For an approved change, define prerequisites, a limited test path, success and stop conditions, monitoring, and rollback. Check Windows DNS roles, Active Directory-integrated data, forwarding paths, time, routing, firewalls, and registrar or registry state in design order. Protect credentials, keys, recovery material, personal data, and sensitive topology in evidence.

Verification and evidence

Evidence should let another reviewer reproduce this decision. Retain observations beside the traced locations Section 3.1 (Selecting Secondary Servers); Section 3.2 (Unsuitable Configurations); Section 5 (How many secondaries?). Favor zone data, packet captures, query transcripts, delegation checks, resolver configuration, and negative-answer behavior, linked to stable identifiers, time, and operator.

Keep before-state evidence, approval, test or change result, exceptions, and after-state evidence together. Use an approved lab, window, or nonproduction path for risky tests. Set a recheck trigger for version, architecture, dependency, vendor, incident, or ownership change. A check proves only what was observed.

Official references

• RFC 2182 — Selection and Operation of Secondary DNS Servers — RFC Editor / Internet Engineering Task Force