dname

DNAME, short for Delegation Name, refers to a DNS resource record type that provides redirection of an entire subtree within the DNS namespace to another domain name. It enables namespace restructuring or migration by mapping all names under a given label to corresponding names under a designated target domain, without requiring updates to each individual record.

How it works in resolution: when a DNS query targets a name that lies within the subtree governed by a DNAME record, resolvers rewrite the query name by replacing the DNAME owner with the specified target, while preserving the remaining labels. Resolution then proceeds against the newly formed name. This mechanism effectively aliases an entire branch of the DNS tree to another domain, similar in spirit to a CNAME but operating at the subtree level rather than on a single name.

Rationale and use cases: DNAME is useful for reorganizing hosting, migrating to a new domain, or delegating an entire subdomain to another organization’s namespace. For example, a DNAME at sub.example.com pointing to target.example.org would redirect queries for any name under sub.example.com to the corresponding name under target.example.org.

Limitations and considerations: DNAME is distinct from CNAME in its scope and interaction with other records; a DNAME cannot be used at the zone apex in many configurations due to how zone data and referrals are managed. Compatibility with DNSSEC, caching behavior, and interaction with NS and glue records can introduce complexity. Not all resolvers and registries support DNAME, and improper use can lead to unresolved queries or inconsistent data across caches. Proper planning and testing are recommended when deploying DNAME records.