What does Windows error code 9971 (DNS_ERROR_POLICY_ALREADY_EXISTS) mean?

DNS_ERROR_POLICY_ALREADY_EXISTS

DNS_ERROR_POLICY_ALREADY_EXISTS means a query-resolution or zone-transfer policy with the same name already exists at the server or zone level where the new policy is being created.

Retrieve the existing policy by name and compare its level, criteria, action, and processing order with the requested definition. Update the intended object or choose a new name instead of creating a duplicate policy blindly.

What to verify

• Check whether the policy is server-level or zone-level; the same intended policy may be looked up at the wrong level.
• Inspect its current action, criteria, processing order, and scope references before modifying it.
• Do not create parallel policies with near-identical names to work around the error; this makes processing order harder to audit.

Get-DnsServerQueryResolutionPolicy
Get-DnsServerQueryResolutionPolicy -ZoneName "example.com"
Get-DnsServerClientSubnet

Microsoft: Get-DnsServerQueryResolutionPolicy

Microsoft: Add-DnsServerQueryResolutionPolicy

Microsoft: DNS Policies overview