What is Azure Bastion?
Azure Bastion is a service you deploy that lets you connect to a virtual machine using your browser and the Azure portal. The Azure Bastion service is a fully platform-managed PaaS service that you provision inside your virtual network. It provides secure and seamless RDP/SSH connectivity to your virtual machines directly from the Azure portal over TLS. When you connect via Azure Bastion, your virtual machines do not need a public IP address, agent, or special client software.
Bastion provides secure RDP and SSH connectivity to all of the VMs in the virtual network in which it is provisioned. Using Azure Bastion protects your virtual machines from exposing RDP/SSH ports to the outside world, while still providing secure access using RDP/SSH.
Azure Bastion deployment is per virtual network, not per subscription/account or virtual machine. Once you provision an Azure Bastion service in your virtual network, the RDP/SSH experience is available to all your VMs in the same virtual network.
RDP and SSH are some of the fundamental means through which you can connect to your workloads running in Azure. Exposing RDP/SSH ports over the Internet isn't desired and is seen as a significant threat surface. This is often due to protocol vulnerabilities. To contain this threat surface, you can deploy bastion hosts (also known as jump-servers) at the public side of your perimeter network. Bastion host servers are designed and configured to withstand attacks. Bastion servers also provide RDP and SSH connectivity to the workloads sitting behind the bastion, as well as further inside the network.
This figure shows the architecture of an Azure Bastion deployment. In this diagram:
- The Bastion host is deployed in the virtual network that contains the AzureBastionSubnet subnet that has a minimum /27 prefix.
- The user connects to the Azure portal using any HTML5 browser.
- The user selects the virtual machine to connect to.
- With a single click, the RDP/SSH session opens in the browser.
- No public IP is required on the Azure VM.
The following features are available:
- RDP and SSH directly in Azure portal: You can directly get to the RDP and SSH session directly in the Azure portal using a single click seamless experience.
- Remote Session over TLS and firewall traversal for RDP/SSH: Azure Bastion uses an HTML5 based web client that is automatically streamed to your local device, so that you get your RDP/SSH session over TLS on port 443 enabling you to traverse corporate firewalls securely.
- No Public IP required on the Azure VM: Azure Bastion opens the RDP/SSH connection to your Azure virtual machine using private IP on your VM. You don't need a public IP on your virtual machine.
- No hassle of managing NSGs: Azure Bastion is a fully managed platform PaaS service from Azure that is hardened internally to provide you secure RDP/SSH connectivity. You don't need to apply any NSGs on Azure Bastion subnet. Because Azure Bastion connects to your virtual machines over private IP, you can configure your NSGs to allow RDP/SSH from Azure Bastion only. This removes the hassle of managing NSGs each time you need to securely connect to your virtual machines.
- Protection against port scanning: Because you do not need to expose your virtual machines to public Internet, your VMs are protected against port scanning by rogue and malicious users located outside your virtual network.
- Protect against zero-day exploits. Hardening in one place only: Azure Bastion is a fully platform-managed PaaS service. Because it sits at the perimeter of your virtual network, you don’t need to worry about hardening each of the virtual machines in your virtual network. The Azure platform protects against zero-day exploits by keeping the Azure Bastion hardened and always up to date for you.
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Do I need a public IP on my virtual machine to connect via Azure Bastion?
No. When you connect to a VM using Azure Bastion, you don't need a public IP on the Azure virtual machine that you are connecting to. The Bastion service will open the RDP/SSH session/connection to your virtual machine over the private IP of your virtual machine, within your virtual network.
Is IPv6 supported?
At this time, IPv6 is not supported. Azure Bastion supports IPv4 only.
Can I use Azure Bastion with Azure Private DNS Zones?
The use of Azure Bastion with Azure Private DNS Zones is not supported at this time. Before you deploy your Azure Bastion resource, please make sure that the host virtual network is not linked to a private DNS zone.
Do I need an RDP or SSH client?
No. You don't need an RDP or SSH client to access the RDP/SSH to your Azure virtual machine in your Azure portal. Use the Azure portal to let you get RDP/SSH access to your virtual machine directly in the browser.
Do I need an agent running in the Azure virtual machine?
No. You don't need to install an agent or any software on your browser or your Azure virtual machine. The Bastion service is agentless and doesn't require any additional software for RDP/SSH.
How many concurrent RDP and SSH sessions does each Azure Bastion support?
Both RDP and SSH are a usage-based protocol. High usage of sessions will cause the bastion host to support a lower total number of sessions. The numbers below assume normal day-to-day workflows.
*These workload types are defined here: Remote Desktop workloads
**These limits are based on RDP performance tests for Azure Bastion. The numbers may vary due to other on-going RDP sessions or other on-going SSH sessions.
What features are supported in an RDP session?
At this time, only text copy/paste is supported. Features, such as file copy, are not supported. Feel free to share your feedback about new features on the Azure Bastion Feedback page.
Does Bastion hardening work with AADJ VM extension-joined VMs?
This feature doesn't work with AADJ VM extension-joined machines using Azure AD users. For more information, see Windows Azure VMs and Azure AD.
Which browsers are supported?
Use the Microsoft Edge browser or Google Chrome on Windows. For Apple Mac, use Google Chrome browser. Microsoft Edge Chromium is also supported on both Windows and Mac, respectively.
Where does Azure Bastion store customer data?
Azure Bastion doesn't move or store customer data out of the region it is deployed in.
Are any roles required to access a virtual machine?
In order to make a connection, the following roles are required:
- Reader role on the virtual machine
- Reader role on the NIC with private IP of the virtual machine
- Reader role on the Azure Bastion resource
What is the pricing?
For more information, see the pricing page.
Does Azure Bastion require an RDS CAL for administrative purposes on Azure-hosted VMs?
No, access to Windows Server VMs by Azure Bastion does not require an RDS CAL when used solely for administrative purposes.
Which keyboard layouts are supported during the Bastion remote session?
Azure Bastion currently supports en-us-qwerty keyboard layout inside the VM. Support for other locales for keyboard layout is work in progress.
Is user-defined routing (UDR) supported on an Azure Bastion subnet?
No. UDR is not supported on an Azure Bastion subnet.
For scenarios that include both Azure Bastion and Azure Firewall/Network Virtual Appliance (NVA) in the same virtual network, you don’t need to force traffic from an Azure Bastion subnet to Azure Firewall because the communication between Azure Bastion and your VMs is private. For more information, see Accessing VMs behind Azure Firewall with Bastion.
Why do I get "Your session has expired" error message before the Bastion session starts?
A session should be initiated only from the Azure portal. Sign in to the Azure portal and begin your session again. If you go to the URL directly from another browser session or tab, this error is expected. It helps ensure that your session is more secure and that the session can be accessed only through the Azure portal.
How do I handle deployment failures?
Review any error messages and raise a support request in the Azure portal as needed. Deployment failures may result from Azure subscription limits, quotas, and constraints. Specifically, customers may encounter a limit on the number of public IP addresses allowed per subscription that causes the Azure Bastion deployment to fail.
How do I incorporate Azure Bastion in my Disaster Recovery plan?
Azure Bastion is deployed within VNets or peered VNets, and is associated to an Azure region. You are responsible for deploying Azure Bastion to a Disaster Recovery (DR) site VNet. In the event of an Azure region failure, perform a failover operation for your VMs to the DR region. Then, use the Azure Bastion host that's deployed in the DR region to connect to the VMs that are now deployed there.
- Tutorial: Create an Azure Bastion host and connect to a Windows VM.
- Learn about some of the other key networking capabilities of Azure.