A domain name system (DNS) server is an example of an information system that provides name/address resolution service. To eliminate single points of failure and to enhance redundancy, there are typically at least two authoritative domain name system (DNS) servers, one configured as primary and the other as secondary. Additionally, the two servers are commonly located in two different network subnets and geographically separated (i.e., not located in the same physical facility). If organizational information technology resources are divided into those resources belonging to internal networks and those resources belonging to external networks, authoritative DNS servers with two roles (internal and external) are established. The DNS server with the internal role provides name/address resolution information pertaining to both internal and external information technology resources while the DNS server with the external role only provides name/address resolution information pertaining to external information technology resources. The list of clients who can access the authoritative DNS server of a particular role is also specified. NIST Special Publication 800-81 provides guidance on secure DNS deployment.