Understanding Azure Virtual Machine Public IP Addressing

When you start an Azure Virtual Machine (VM) instance, you will get a Public IP Address. This allows you to remote-desktop into the Azure VM instance. Naturally, you may try to reconnect back with the same IP Address at a later time after you disconnect from it. However, if you are using the default setting of dynamic IP, the old IP would not work since a new IP would be assigned.

There are two approaches to trying to solve/minimize the problem of reconnecting without changing the Remote Desktop Connection.

If you navigate to the Public IP Address page on the Azure portal, you will find 2 options:

Option 1:

You can setup a static IP Address. This approach means you can always rely on a known IP Address. This is a good choice especially if you have some firewall configuration that relies on a known static IP Address.

Whether you choose to go with dynamic or static, please take note of the pricing implications.

Option 2:

Setup a FQDN (fully-qualified domain name). This approach means you don't have to worry about choosing between dynamic or static IP address. You can either choose to use the default of providing a unique name as a prefix to Azure's domain name i.e. [Your_Name].southcentralus.cloudapp.azure.com as in my example screenshot, or choose to use your own domain name.

If you choose to use your own domain name, please take note of the pricing implications.

Idle timeout caveat

In cases where you have a period of inactivity, your initial public IP address would be unassigned. This could happen if there's no keep-alive messages. As such, one technique is to increase the Idle timeout. This approach does not completely solve the issue because at some point, the inactivity would still cause the Public IP to change. However, it is still a useful configuration to know about since you cannot turned Idle timeout off. By default the minimum Idle timeout setting is 4 minutes.

I hope this helps you in understanding more about Azure Virtual Machine Public IP Addressing.