Database Availability Group (DAG) uses an IP address assigned by a DHCP server by default. Please check my previous articles about configuring DAG and points to note if you are not familiar with DAG. You can use the exchange console or the shell to configure the properties of a DAG, including the witness server and directory used by the DAG. The shell enables you to configure the DAG properties that are not available in the console. As an administrator, you can assign a static IP address for the DAG, though it is not a requirement. DAG doesn’t really care as long as it has an IP address and the name of the DAG is resolvable. The DAG name is not used by users or admins anyway. It is only used by the system for internal communication.
To find the current ip address of the DAG, run the command
Get-DatabaseAvailabilityGroup -identity "dagname" | fl *ip*
To configure a static IP address (say 192.168.1.104) for the DAG, run
Set-DatabaseAvailabilityGroup -identity "dagname" -DatabaseAvailabilityGroupIpAddress 192.168.1.104
If you have a DAG that spans multiple subnets (for high availability), you can configure multiple ip addresses for the DAG. To configure multiple ip addresses, run
Set-DatabaseAvailabilityGroup -identity "dagname" -DatabaseAvailabilityGroupIpAddress 192.168.1.104, 192.168.2.104