What does Windows error code 9707 (DNS_ERROR_CNAME_LOOP) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: A circular CNAME alias chain was detected.

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DNS_ERROR_NAME_NOT_IN_ZONE	DNS_ERROR_NODE_IS_CNAME

DNS_ERROR_CNAME_LOOP

DNS_ERROR_CNAME_LOOP means following CNAME aliases leads back to a name already visited. Resolvers cannot produce a stable canonical answer from a circular alias chain.

What to check

Trace the CNAME chain from the failing name until it repeats.
Correct the alias that closes the loop and point it at a real canonical record instead.
Check deployment automation for reciprocal aliases created by renames or failover scripts.

Resolve-DnsName -Name "alias.contoso.com" -Server "dns-server" -DnsOnly

Microsoft: Get-DnsServerResourceRecord

Microsoft: DNS architecture, SOA, and authoritative zones

Microsoft: DNS logging and diagnostics

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