Reverse DNS
Discover the VM DNS name with reverse DNS.
Create a VM:
az vm create -n 'vm-az104' -g 'rg-az104' --image 'UbuntuLTS' --admin-user 'azureuser' --admin-password 'AwsomeAz104!'
Connect to it and run the command:
dig -x 10.0.0.4 +short
The response will be: vm-az104.internal.cloudapp.net.