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About Bastion configuration settings

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The sections in this article discuss the resources and settings for Azure Bastion.

SKUs

A SKU is also known as a Tier. Azure Bastion supports multiple SKU tiers. When you configure Bastion, you select the SKU tier. You decide the SKU tier based on the features that you want to use. The following table shows the availability of features per corresponding SKU.

Feature Developer SKU Basic SKU Standard SKU
Connect to target VMs in same virtual network Yes Yes Yes
Connect to target VMs in peered virtual networks No Yes Yes
Support for concurrent connections No Yes Yes
Access Linux VM Private Keys in Azure Key Vault (AKV) No Yes Yes
Connect to Linux VM using SSH Yes Yes Yes
Connect to Windows VM using RDP Yes Yes Yes
Connect to Linux VM using RDP No No Yes
Connect to Windows VM using SSH No No Yes
Specify custom inbound port No No Yes
Connect to VMs using Azure CLI No No Yes
Host scaling No No Yes
Upload or download files No No Yes
Kerberos authentication No Yes Yes
Shareable link No No Yes
Connect to VMs via IP address No No Yes
VM audio output Yes Yes Yes
Disable copy/paste (web-based clients) No No Yes

Developer SKU (Preview)

The Bastion Developer SKU is a new, lower-cost, lightweight SKU. This SKU is ideal for Dev/Test users who want to securely connect to their VMs and that don't need additional features or scaling. You can connect to one Azure VM at a time directly through the Virtual Machine connect page.

The Developer SKU has different requirements and limitations than the other SKU tiers. See Deploy Bastion automatically - Developer SKU for more information and deployment steps.

The Developer SKU (Preview) is currently available in the following regions:

  • Central US EUAP
  • East US 2 EUAP
  • West Central US
  • North Central US
  • West US
  • North Europe

Note

VNet peering isn't currently supported for the Developer SKU.

Specify SKU

Method SKU Value Links
Azure portal Tier - Developer Quickstart
Azure portal Tier - Basic Quickstart
Azure portal Tier - Basic or Standard Tutorial
Azure PowerShell Tier - Basic or Standard How-to
Azure CLI Tier - Basic or Standard How-to

Upgrade a SKU

You can always upgrade a SKU to add more features.

Note

Downgrading a SKU is not supported. To downgrade, you must delete and recreate Azure Bastion.

You can configure this setting using the following method:

Method Value Links
Azure portal Tier How-to

Azure Bastion subnet

Important

For Azure Bastion resources deployed on or after November 2, 2021, the minimum AzureBastionSubnet size is /26 or larger (/25, /24, etc.). All Azure Bastion resources deployed in subnets of size /27 prior to this date are unaffected by this change and will continue to work, but we highly recommend increasing the size of any existing AzureBastionSubnet to /26 in case you choose to take advantage of host scaling in the future.

When you deploy Azure Bastion using any SKU except the Developer SKU, Bastion requires a dedicated subnet named AzureBastionSubnet. You must create this subnet in the same virtual network that you want to deploy Azure Bastion to. The subnet must have the following configuration:

  • Subnet name must be AzureBastionSubnet.
  • Subnet size must be /26 or larger (/25, /24 etc.).
  • For host scaling, a /26 or larger subnet is recommended. Using a smaller subnet space limits the number of scale units. For more information, see the Host scaling section of this article.
  • The subnet must be in the same virtual network and resource group as the bastion host.
  • The subnet can't contain other resources.

You can configure this setting using the following methods:

Method Value Links
Azure portal Subnet Quickstart
Tutorial
Azure PowerShell -subnetName cmdlet
Azure CLI --subnet-name command

Public IP address

Azure Bastion deployments require a Public IP address, except Developer SKU deployments. The Public IP must have the following configuration:

  • The Public IP address SKU must be Standard.
  • The Public IP address assignment/allocation method must be Static.
  • The Public IP address name is the resource name by which you want to refer to this public IP address.
  • You can choose to use a public IP address that you already created, as long as it meets the criteria required by Azure Bastion and isn't already in use.

You can configure this setting using the following methods:

Method Value Links
Azure portal Public IP address Azure portal
Azure PowerShell -PublicIpAddress cmdlet
Azure CLI --public-ip create command

Instances and host scaling

An instance is an optimized Azure VM that is created when you configure Azure Bastion. It's fully managed by Azure and runs all of the processes needed for Azure Bastion. An instance is also referred to as a scale unit. You connect to client VMs via an Azure Bastion instance. When you configure Azure Bastion using the Basic SKU, two instances are created. If you use the Standard SKU, you can specify the number of instances (with a minimum of two instances). This is called host scaling.

Each instance can support 20 concurrent RDP connections and 40 concurrent SSH connections for medium workloads (see Azure subscription limits and quotas for more information). The number of connections per instances depends on what actions you're taking when connected to the client VM. For example, if you're doing something data intensive, it creates a larger load for the instance to process. Once the concurrent sessions are exceeded, another scale unit (instance) is required.

Instances are created in the AzureBastionSubnet. To allow for host scaling, the AzureBastionSubnet should be /26 or larger. Using a smaller subnet limits the number of instances you can create. For more information about the AzureBastionSubnet, see the subnets section in this article.

You can configure this setting using the following methods:

Method Value Links Requires Standard SKU
Azure portal Instance count How-to Yes
Azure PowerShell ScaleUnit How-to Yes

Custom ports

You can specify the port that you want to use to connect to your VMs. By default, the inbound ports used to connect are 3389 for RDP and 22 for SSH. If you configure a custom port value, specify that value when you connect to the VM.

Custom port values are supported for the Standard SKU only.

The Bastion Shareable Link feature lets users connect to a target resource using Azure Bastion without accessing the Azure portal.

When a user without Azure credentials clicks a shareable link, a webpage opens that prompts the user to sign in to the target resource via RDP or SSH. Users authenticate using username and password or private key, depending on what you have configured in the Azure portal for that target resource. Users can connect to the same resources that you can currently connect to with Azure Bastion: VMs or virtual machine scale set.

Method Value Links Requires Standard SKU
Azure portal Shareable Link Configure Yes

Next steps

For frequently asked questions, see the Azure Bastion FAQ.