Windows error 9721 (DNS_ERROR_DNAME

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: a DNAME already exists at the requested owner name and conflicts with the proposed DNS record change.

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DNS_ERROR_NODE_IS_DNAME	DNS_ERROR_ALIAS_LOOP

DNS_ERROR_DNAME_COLLISION

The requested RRset collides with an existing DNAME

DNAME is a subtree redirection record. RFC 6672 notes that adding a DNAME occludes descendant names and defines special alias processing for names below the owner. Because the DNAME changes how an entire branch is resolved, an update that tries to establish incompatible owner or descendant data can be rejected as a collision.

Inspect both the existing DNAME and the exact RRset being added. A duplicate DNAME target change should use an update operation; an unrelated record below the DNAME belongs elsewhere; and an attempt to replace the redirection requires a planned removal of DNAME before direct data is introduced. Do not treat this as the same collision as CNAME, which aliases a single owner.

What to inspect

Enumerate the owner node and locate the existing DNAME RDATA.
Classify the requested update as DNAME replacement, same-owner data, or descendant data.
Apply the appropriate update or namespace migration instead of retrying the same add.

References

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