Azure Bastion Deep Dive


Azure Bastion Deep Dive: Secure, Seamless RDP & SSH Access to Azure VMs

Meta Description: Explore Azure Bastion’s architecture, real-world implementation, and security best practices. Learn how to deliver secure, agentless remote access to Azure VMs without public IPs—directly from a senior IT professional with 10+ years of hands-on experience.


Introduction

After more than a decade designing, securing, and administering enterprise IT environments—both on-prem and in the cloud—I've seen firsthand how critical secure remote access is for virtual machine administration. The need to provide robust, seamless access to VMs, while minimizing exposure to threats and brute-force attacks, has always been a balancing act.

One of the most game-changing solutions in Microsoft Azure’s arsenal is Azure Bastion. This fully managed platform service provides secure and seamless RDP and SSH connectivity to your Azure virtual machines directly in the Azure portal—without the need for public IP addresses or jump boxes. In this blog, I’ll walk you through the technical features, real-world deployment, security considerations, and best practices for Azure Bastion, based on actual production experience across diverse enterprise environments.


What is Azure Bastion?

Azure Bastion is a fully managed PaaS (Platform as a Service) that enables secure and seamless remote desktop (RDP) and SSH access to VMs within your virtual network. Unlike traditional jump servers or exposing VM endpoints to the public internet, Bastion abstracts the connectivity layer and provides browser-based and native client access without exposing a single public IP.

This means you can administer your Linux and Windows Azure VMs securely, reducing your attack surface and eliminating the headaches of managing public RDP/SSH endpoints.


Core Features and Architecture

  • Feature: Agentless, browser-based RDP and SSH access to VMs via Azure Portal

  • Benefit: Eliminates need for public IPs on VMs, reducing attack vectors

  • Permissions: Azure RBAC integration controls who can access Bastion and underlying VMs

  • Backup: No persistent data on Bastion host; session activity can be logged via Azure Monitor and Sentinel


Why Secure Remote Access Matters

Traditional RDP and SSH exposure is a top cause of cloud breaches—attackers continuously scan for open ports and weak credentials. In hybrid and cloud environments, securing remote access without hindering productivity is a real challenge. Azure Bastion’s architecture is specifically designed to address these security pitfalls:

  • No public IP required for VM access

  • All traffic remains within Azure’s trusted backbone

  • Zero standing endpoint exposure


Azure Bastion Architecture: How It Works

When you deploy Azure Bastion, a managed instance is provisioned within your Azure Virtual Network (VNet), attached to a dedicated subnet named BastionSubnet. Administrators connect to this service via the Azure portal (or via native RDP/SSH clients if Bastion Premium is enabled), and Bastion brokers the session directly to your target VM over private IP—never traversing the public internet.

This model ensures that RDP and SSH ports can remain closed to the outside world, while still allowing authorized users to connect on-demand.


Azure Bastion Architecture Diagram

ALT: Azure Bastion Service architecture diagram showing secure connectivity between user, Bastion, and Azure VM


Step-by-Step Implementation: Deploying Azure Bastion

Let’s walk through a typical deployment scenario—from prerequisites to first connection—with commentary based on real-world enterprise projects.


1. Prerequisites

  • Feature: Existing Virtual Network (VNet) and at least one VM

  • Benefit: Allows integration of Bastion into current infrastructure without redesign

  • Permissions: Owner or Contributor role on the VNet resource group

  • Backup: VNet and VM configurations can be exported as ARM templates


2. Provisioning the Bastion Host

  • Feature: Azure Bastion resource deployed into a dedicated BastionSubnet (minimum /26 subnet mask)

  • Benefit: Isolates Bastion from other subnets, aligning with least privilege network segmentation

  • Permissions: Must have permission to create subnets and deploy resources

  • Backup: Bastion settings can be exported via ARM/Bicep for disaster recovery


3. Enabling Bastion Access

  • Feature: Users connect via the Azure Portal or, with Bastion Premium, via a native client

  • Benefit: Browser-based access is OS-agnostic; no RDP/SSH client installations required

  • Permissions: Bastion Reader/Contributor and VM login permissions via Azure RBAC

  • Backup: Connection logs can be sent to Azure Monitor for auditing


4. Connecting to a VM

  • Feature: Select a VM in the portal, click “Connect”, and choose Bastion

  • Benefit: Seamless, instant connectivity—no need for VPN or jump servers

  • Permissions: VM-level login credentials required (local or Azure AD-based)

  • Backup: Audit logs can document who accessed which VM and when


Enterprise-Grade Features: Azure Bastion Standard vs Premium

Microsoft now offers two Bastion SKUs—Standard and Premium (formerly Basic and Standard). Here’s a breakdown of the advanced capabilities that make Bastion scalable for large organizations:

  • Feature: Native client support (Premium SKU) for RDP/SSH

  • Benefit: Enables integration with credential managers and advanced session features

  • Permissions: Requires Bastion Premium deployment and corresponding user permissions

  • Backup: Premium Bastion settings can be exported as code for redeployment

  • Feature: IP-based connection (Premium), allowing access by private IP

  • Benefit: Supports more flexible, hybrid, and peered network topologies

  • Permissions: Network-level RBAC required for cross-VNet access

  • Backup: Connection policies and NSGs should be documented and backed up

  • Feature: Session recording and auditing via Azure Monitor/Sentinel

  • Benefit: Enterprise-grade compliance and forensics

  • Permissions: Logging permissions in Azure Monitor/Log Analytics workspace

  • Backup: Log retention policies can be set for regulatory compliance


Security Best Practices with Azure Bastion

Over the years, I’ve developed a set of practical best practices for securing Bastion deployments in the field:

  • Feature: No public IPs assigned to VMs

  • Benefit: Minimizes external attack surface

  • Permissions: Remove unnecessary “Owner” or “Contributor” rights on VMs

  • Backup: Regularly export RBAC assignments for review</

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