Environment: Exchange Server 2019 Exchange 2013 exists Forest functional level – 2016 Exchange Server OS – Server 2019 Exchange servers are VMs (vSphere 6.7) Hey team, got an odd error here when my customer runs “Add-DatabaseAvailabilityGroupServer” for the first server being added to a 2019 DAG: [2020-10-06T21:22:34] The operation wasn't successful because an error was encountered. You may find more details in log file "C:\ExchangeSetupLogs\DagTasks\dagtask_2020-10-06_21-19-28.923_add-databaseavailabiltygroupserver.log" on "XXXX-EX19A1-X". (the log is attached) [2020-10-06T21:22:34] WriteError! Exception = Microsoft.Exchange.Cluster.Replay.DagTaskOperationFailedException: A server-side database availability group administrative operation failed. Error The operation failed. CreateCluster errors may result from incorrectly configured static addresses. Error: An error occurred while attempting a cluster operation. Error: Cluster API failed: "CreateCluster() failed with 0x42a. Error: The service has returned a service-specific error code". ---> [30752-error-dag.txt][1] When I look up further in the log that the error mentions, I see the error code mentioned: [2020-10-06T21:22:34] ClusterSetupProgressCallback( eSetupPhase = ClusterSetupPhaseFormingCluster, ePhaseType = ClusterSetupPhaseEnd, ePhaseSeverity = ClusterSetupPhaseFatal, dwPercentComplete = 56, szObjectName = xxxx-daga-x, dwStatus = 0x42a ) We tried adding a different server first, but same error occurs. I’ve seen a couple of links mentioning permissions/configurations on the CNO and duplicate MACs, but all those things are set correctly as well. We’ve also tried removing and re-creating the DAG (with the same name and with a different name) without an IP without success. At first, we were getting an error about Failover Clustering not being installed. We checked that and it said a restart was pending, so we restarted and now we get this error above. Also in the log, it mentions the DAG CNO doesn’t exist, but it does. Screenshots show the command we ran and where it sticks, then the second shows the error message that comes up afterward. Anyone got any ideas? ![30773-screenshot.png][2]![30783-failedscreenshot.png][3] [1]: /answers/storage/attachments/30752-error-dag.txt [2]: /answers/storage/attachments/30773-screenshot.png [3]: /answers/storage/attachments/30783-failedscreenshot.png