1. Login into Azure portal on https://portal.azure.com and navigate to Virtual machines section.
2. Click on the one you would like to manage.
3. Obtain the following information:
- IP Address Name
4. Make sure that the IP address is set up to Static and the DNS name is specified.
5. Open Cloud Shell on the right-upper corner as shown below:
6. Run the following commands:
$pip = Get-AzureRmPublicIpAddress -Name "PublicIp" -ResourceGroupName "MyResourceGroup"
$pip.DnsSettings.reverseFqdn = "your.rdnsrecord.com"
Set-AzureRmPublicIpAddress -PublicIpAddress $pip