I'm assuming this is a DC running on a VM and you have other DC's in on-premises locations also. Need to know a little more about the setup here to confirm, such as what you are using for connectivity between Azure IaaS and your on-premises network, but my 'gut-feel' answer is that you need to take a look at AD Sites and Services and ensure that you have mapped all your subnets correctly to the physical and logical locations on your network. Could it be that the DC on the VM in Azure is authenticating users at a remote location?
Azure domain controller VM consuming high bandwidth

Sandeep Kumar
1
Reputation point
We have configured one domain controller with Azure ad connect but the bandwidth consumption (Upload/sent) is very high. Due to this, our cost is going high.
How to resolve this?