Introduction

Sometimes when adding member servers to a DAG you might encounter the following error message:

“Network name <DAG> is not online. Please check that the IP address configuration for the database availability group is correct“:

Solution

There are different reasons why you might encounter this issue. However, the two most common causes are:

1. Not all necessary firewall ports are open, causing connectivity issues when adding members.
2. Active Directory replication did not (yet) occur.

For now, we’ll focus on the Directory replication part.

You will probably be presented with this error if you created the DAG and you try adding member servers (from another AD site) directly afterwards, but before AD replication between both sites got the chance to occur.

The second AD-site (and thus the second/third/…) server that is in that AD site does not necessarily know about the DAG (yet) resulting in the warning above.

You’ll notice that if you run the Get-DatabaseAvailabilityGroupNetwork cmdlet on the remote server, you might get an error:

To overcome these (temporary) issues, you should force replication between both sites after which everything turns back to normal:

Alternatively, you can wait for AD replication to occur automatically. The time that is needed depends on how your replication scheme is defined.