Control statement
Ensure the systems that collectively provide name/address resolution service for an organization are fault-tolerant and implement internal and external role separation.
Discussion
Systems that provide name and address resolution services include domain name system (DNS) servers. To eliminate single points of failure in systems and enhance redundancy, organizations employ at least two authoritative domain name system servers—one configured as the primary server and the other configured as the secondary server. Additionally, organizations typically deploy the servers in two geographically separated network subnetworks (i.e., not located in the same physical facility). For role separation, DNS servers with internal roles only process name and address resolution requests from within organizations (i.e., from internal clients). DNS servers with external roles only process name and address resolution information requests from clients external to organizations (i.e., on external networks, including the Internet). Organizations specify clients that can access authoritative DNS servers in certain roles (e.g., by address ranges and explicit lists).
From control text to operational evidence
Use Architecture and Provisioning for Name/Address Resolution Service as a testable risk decision. Translate the official statement into accountable people, repeatable processes, configured technology, and evidence that demonstrates the outcome over time. In this family, pay particular attention to secure architecture, boundary protection, communications protection, cryptography, and system isolation.
Implementation workflow
- Define the control boundary, responsible owner, inherited portions, and systems or processes in scope.
- Resolve each organization-defined parameter before declaring the control implemented.
- Document how the implementation satisfies every clause of the official control statement.
- Collect evidence as a normal byproduct of operation rather than only before an assessment.
- Review exceptions, changes, and monitoring results on a risk-based cadence.
Evidence examples
- network and trust-boundary diagrams
- firewall and gateway configurations
- cryptographic configuration and key records
- segmentation and isolation test results
Common failure patterns
- diagrams omit cloud and third-party paths
- encryption enabled without key governance
- flat trust zones allow unnecessary lateral movement
- boundary rules accumulate without owner review
Questions practitioners should ask
- What risk decision is this control intended to support in this system?
- Which parts are implemented locally, inherited, shared, or not applicable—and what evidence supports that decision?
- Do the documented narrative, deployed configuration, operating process, and collected evidence agree?
- What event or threshold requires the implementation to be reviewed or changed?
Assessment objectives and methods
Show the assessment objective
- SC-22[01]the systems that collectively provide name/address resolution services for an organization are fault-tolerant;
- SC-22[02]the systems that collectively provide name/address resolution services for an organization implement internal role separation;
- SC-22[03]the systems that collectively provide name/address resolution services for an organization implement external role separation.
Examine
- System and communications protection policy
- procedures addressing architecture and provisioning for name/address resolution services
- access control policy and procedures
- system design documentation
- assessment results from independent testing organizations
- system configuration settings and associated documentation
- system audit records
- system security plan
- other relevant documents or records
Interview
- System/network administrators
- organizational personnel with information security responsibilities
- organizational personnel with responsibilities for managing DNS
Test
- Mechanisms supporting and/or implementing name/address resolution services for fault tolerance and role separation
Related controls
These relationships come from the official OSCAL catalog. They indicate useful dependencies or context, not automatic inheritance or equivalence.
Authoritative sources
Bare Metal Cyber is an independent educational publisher and is not affiliated with or endorsed by NIST. Official control requirements and interpretations remain with NIST and the responsible authorizing organization.