DNS did not move correctly after name server change

If the name servers changed but resolution did not fully move, check these items in order:

1. Verify the Azure DNS zone contents. In the Azure portal, confirm the zone name, record names, and record types were imported correctly. A common issue is that the NS delegation changed, but the target zone in Azure is missing records or has incorrect names.
2. Test the Azure DNS name servers directly. Query the Azure-assigned name servers for the fully qualified record name and correct record type. This confirms whether Azure DNS is serving the expected records.
3. Confirm delegation at the registrar is complete. The domain must be delegated to the Azure DNS name servers shown in the Azure portal. If delegation is incomplete or still points partly to the old provider, resolution can be inconsistent.
4. Avoid split delegation between old and new providers. Keeping some name servers on the old provider and some on Azure can cause intermittent failures because resolvers may query either set. The zone data must be identical during transition, or delegation should be switched cleanly to the Azure DNS name servers.
5. Flush caches and retest. If records were recently changed, cached results can make it look like the move failed. On Windows:

      ipconfig /flushdns
      Clear-DnsClientCache
   

6. Compare resolution paths. From a Windows client, first see which resolver is being used:

      Get-DnsClientServerAddress -AddressFamily IPv4
      ipconfig /all | Select-String "DNS Servers"
   

   Then test resolution:

      Resolve-DnsName www.contoso.com
      Resolve-DnsName www.contoso.com -Server 1.1.1.1
   

   If the public resolver sees the new records but the default resolver does not, that points to caching or an upstream resolver delay.
7. If queries time out instead of returning old data, test port 53 reachability.

      Test-NetConnection 168.63.129.16 -Port 53
   

   In Azure, also review effective NSG rules on the VM NIC and confirm outbound UDP and TCP 53 are allowed to the DNS server being queried.

If the Azure name servers answer correctly for the records, but some clients still see old results after only a few hours, that is consistent with propagation or caching. If the Azure name servers do not answer correctly, the issue is configuration or delegation rather than propagation.

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