Add session hosts to a host pool

After you create a host pool, a workspace, and an application group, you need to add session hosts to the host pool for your users to connect to. You might also need to add more session hosts for extra capacity.

You can create new virtual machines (VMs) to use as session hosts and add them to a host pool natively by using the Azure Virtual Desktop service in the Azure portal. Alternatively, you can create VMs outside the Azure Virtual Desktop service, such as using an automated pipeline, the Azure CLI, or Azure PowerShell, and then add them as session hosts to a host pool separately.

This article shows you how to generate a registration key by using the Azure portal, the Azure CLI, or Azure PowerShell. It also shows you how to add session hosts to a host pool by using the Azure Virtual Desktop service or add them to a host pool separately.

Prerequisites

For a general idea of what's required, such as supported operating systems, virtual networks, and identity providers, review the prerequisites for Azure Virtual Desktop. In addition:

• You need an existing host pool. You can't mix session hosts on Azure, or Azure Stack HCI in the same host pool.

• If you have existing session hosts in the host pool, make a note of the virtual machine size, the image, and name prefix that you used. All session hosts in a host pool should have the same configuration, including the same identity provider. For example, a host pool shouldn't contain some session hosts joined to Microsoft Entra ID and some session hosts joined to an Active Directory domain.

• The Azure account you use must have the following built-in role-based access control (RBAC) roles or equivalent as a minimum on the resource group:

  Action	RBAC role or roles
  Generate a registration key for the host pool	Desktop Virtualization Host Pool Contributor
  Create and add session hosts using the Azure portal	Desktop Virtualization Host Pool Contributor Virtual Machine Contributor

• Don't disable Windows Remote Management (WinRM) when you're creating and adding session hosts by using the Azure portal. PowerShell DSC requires it.

• If you want to use Azure CLI or Azure PowerShell locally, see Use Azure CLI and Azure PowerShell with Azure Virtual Desktop to make sure you have the desktopvirtualization Azure CLI extension or the Az.DesktopVirtualization PowerShell module installed.

Generate a registration key

When you add session hosts to a host pool, first you need to generate a registration key for that host pool. A registration key authorizes session hosts to join the host pool. It's valid only for the duration that you specify.

To generate a registration key, select the relevant tab for your scenario and follow the steps.

Create and register session hosts with the Azure Virtual Desktop service

You can create session hosts and register them to a host pool in a single end-to-end process with the Azure Virtual Desktop service by using the Azure portal or an Azure Resource Manager template (ARM template). You can find some example ARM templates in this GitHub repo.

Here's how to create session hosts and register them to a host pool by using the Azure Virtual Desktop service in the Azure portal. Make sure that you generated a registration key first.

1. Sign in to the Azure portal.

2. On the search bar, enter Azure Virtual Desktop and select the matching service entry.

3. Select Host pools, and then select the name of the host pool to which you want to add session hosts.

4. On the host pool overview, select Session hosts, and then select + Add.

5. The Basics tab is unavailable because you're using the existing host pool. Select Next: Virtual Machines.

6. On the Virtual machines tab, complete the information. For guidance on sizing session host virtual machines, see Session host virtual machine sizing guidelines.
   
   

   Parameter	Value/Description
   Resource group	This value defaults to the same resource group as your host pool, but you can select a different one from the dropdown list.
   Name prefix	Enter a name prefix for your session hosts, such as hp01-sh. Each session host has a suffix of a hyphen and then a sequential number added to the end, such as hp01-sh-0. This name prefix can be a maximum of 11 characters and is used in the computer name in the operating system. The prefix and the suffix combined can be a maximum of 15 characters. Session host names must be unique.
   Virtual machine location	Select the Azure region where you want to deploy your session hosts. It must be the same region that contains your virtual network.
   Availability options	Select from availability zones, availability set, or No infrastructure redundancy required. If you select availability zones or availability set, complete the extra parameters that appear.
   Security type	Select from Standard, or Trusted launch virtual machines. - If you select Trusted launch virtual machines, options for secure boot and vTPM are automatically selected.
   Image	Select the OS image that you want to use from the list, or select See all images to see more. The full list includes any images that you created and stored as an Azure Compute Gallery shared image or a managed image.
   Virtual machine size	Select a size. If you want to use a different size, select Change size, and then select from the list.
   Number of VMs	Enter the number of virtual machines that you want to deploy. You can deploy up to 400 session hosts at this point if you want (depending on your subscription quota), or you can add more later. For more information, see Azure Virtual Desktop service limits and Virtual Machines limits.
   OS disk type	Select the disk type to use for your session hosts. We recommend that you use only Premium SSD for production workloads.
   Boot Diagnostics	Select whether you want to enable boot diagnostics.
   Network and security
   Virtual network	Select your virtual network. An option to select a subnet appears.
   Subnet	Select a subnet from your virtual network.
   Network security group	Select whether you want to use a network security group (NSG). - None doesn't create a new NSG. - Basic creates a new NSG for the VM network adapter. - Advanced enables you to select an existing NSG. We recommend that you don't create an NSG here, but create an NSG on the subnet instead.
   Public inbound ports	You can select a port to allow from the list. Azure Virtual Desktop doesn't require public inbound ports, so we recommend that you select No.
   Domain to join
   Select which directory you would like to join	Select from Microsoft Entra ID or Active Directory and complete the relevant parameters for the selected option. To learn more about joining session hosts to Microsoft Entra ID, see Microsoft Entra joined session hosts.
   Virtual Machine Administrator account
   Username	Enter a name to use as the local administrator account for the new session hosts.
   Password	Enter a password for the local administrator account.
   Confirm password	Reenter the password.
   Custom configuration
   Custom configuration script URL	If you want to run a PowerShell script during deployment, you can enter the URL here.

   After you complete this tab, select Next: Tags.

7. On the Tags tab, you can optionally enter any name/value pairs that you need, and then select Next: Review + create.

8. On the Review + create tab, ensure that validation passes and review the information that will be used during deployment. If validation doesn't pass, review the error message and check what you entered on each tab.

9. Select Create. After your deployment is complete, the session hosts should appear in the host pool.

Register session hosts to a host pool

If you created virtual machines by using an alternative method outside Azure Virtual Desktop, such as an automated pipeline, you need to register them separately as session hosts to a host pool.

To register session hosts to a host pool, you need to install the Azure Virtual Desktop Agent and the Azure Virtual Desktop Agent Boot Loader on each virtual machine and use the registration key that you generated. You can register session hosts to a host pool by using the agent installers' graphical user interface (GUI) or by using msiexec from a command line.

After you finish, four applications are listed as installed applications:

• Remote Desktop Agent Boot Loader
• Remote Desktop Services Infrastructure Agent
• Remote Desktop Services Infrastructure Geneva Agent
• Remote Desktop Services SxS Network Stack

Select the relevant tab for your scenario and follow the steps.

Post-deployment tasks

After you add session hosts to your host pool, you might need to do some extra configuration, as described in the following sections.

Licensing

To ensure that your session hosts have licenses applied correctly, you need to do the following tasks:

• If you have the correct licenses to run Azure Virtual Desktop workloads, you can apply a Windows or Windows Server license to your session hosts as part of Azure Virtual Desktop and run them without paying for a separate license. This license is automatically applied when you create session hosts by using the Azure Virtual Desktop service, but you might have to apply the license separately if you create session hosts outside Azure Virtual Desktop. For more information, see Apply a Windows license to session host virtual machines.

• If your session hosts are running a Windows Server OS, you also need to issue them a Remote Desktop Services (RDS) client access license (CAL) from an RDS license server. For more information, see License your RDS deployment with client access licenses.

• For session hosts on Azure Local, you must license and activate the virtual machines before you use them with Azure Virtual Desktop. For activating VMs that use Windows 10 Enterprise multi-session, Windows 11 Enterprise multi-session, and Windows Server 2022 Datacenter: Azure Edition, use Azure verification for VMs. For all other OS images (such as Windows 10 Enterprise, Windows 11 Enterprise, and other editions of Windows Server), you should continue to use existing activation methods. For more information, see Activate Windows Server VMs on Azure Local.

Microsoft Entra joined session hosts

For session hosts on Azure that are joined to Microsoft Entra ID, you also need to enable single sign-on or earlier authentication protocols, assign an RBAC role to users, and review your multifactor authentication policies so that users can sign in to the VMs. For more information, see Microsoft Entra joined session hosts.

Related content

Now that you've expanded your existing host pool, you can sign in to an Azure Virtual Desktop client to test the hosts as part of a user session. You can connect to a session by using any of the following clients:

• Connect with the Windows desktop client
• Connect with the web client
• Connect with the iOS client