Microsoft is changing how outbound internet access works in Azure—and it’s a big deal for anyone managing virtual networks in the cloud.
As of September 30, 2025, default outbound access will no longer be available for new virtual networks. This means that virtual machines (VMs) deployed in those networks won’t have internet access unless you explicitly define how they reach the internet. The good news? Azure Private Subnets are now generally available and designed to help with the transition.
What Are Azure Private Subnets?
Private Subnets in Azure are subnets that do not allow default outbound internet access. By using them, you can enforce more secure networking practices and ensure that any internet access is intentional, logged, and controlled.
Here’s how Azure VMs traditionally gain outbound internet access:
– Through a user-defined route to an appliance like Azure Firewall or a third-party NVA
– Via a connected NAT Gateway
– By using a Public IP address assigned to the VM’s NIC
– Through a load balancer with outbound rules
– Or, if none of the above are defined, via default outbound access from a Microsoft-managed public IP (this is what’s going away)
This implicit access might be convenient, but it lacks transparency and control. That’s why Microsoft is deprecating it in favor of explicit internet routing.
Why This Change Matters
If your workloads require outbound connectivity—for example, to reach Windows Update or activation services—they will fail in a Private Subnet unless you’ve configured an explicit outbound path like a NAT Gateway or firewall.
Private Subnets give you the control to:
– Define your outbound traffic path
– Use static IPs for better tracking and security
– Comply with tighter security and audit requirements
And starting late 2025, all new subnets will default to Private Subnets, so the time to prepare is now.
How to Get Started
You can create a new Private Subnet by selecting the “Private Subnet” option when creating or modifying a subnet in the Azure portal. You can also convert an existing subnet to a Private Subnet to begin phasing out default access.
To enable outbound access in a Private Subnet, the simplest method is to configure a NAT Gateway.
📺 Watch the step-by-step video tutorial on how to create Private Subnets and NAT Gateways in new and existing VNets here:
Key Reminders
– NAT Gateways can serve multiple subnets in the same VNet, but each NAT Gateway can only be connected to one VNet.
– Delegated or managed subnets for PaaS services should not use Private Subnets, as those services manage outbound access themselves.
– User-defined routes that bypass system routes can cause issues in Private Subnets if service-tagged destinations are required.
By preparing now, you’ll not only stay ahead of the 2025 deadline but also build a more secure and predictable network environment. Start exploring Azure Private Subnets today and take full control over how your workloads connect to the internet.
Links:
Zero to Hero with Azure Virtual Desktop
https://www.udemy.com/course/zero-to-hero-with-windows-virtual-desktop/?referralCode=B2FE49E6FCEE7A7EA8D4
Hybrid Identity with Windows AD and Azure AD
https://www.udemy.com/course/hybrid-identity-and-azure-active-directory/?referralCode=7F62C4C6FD05C73ACCC3
Windows 365 Enterprise and Intune Management
https://www.udemy.com/course/windows-365-enterprise-and-intune-management/?referralCode=4A1ED105341D0AA20D2E
Default Outbound Access in Azure
https://learn.microsoft.com/en-us/azure/virtual-network/ip-services/default-outbound-access?WT.mc_id=AZ-MVP-5004159
