Share via

AzureFirewallManagementSubnet: must default outbound access be enabled?

Pittl Benedikt (INFRA.IT) 20 Reputation points
2026-04-15T19:55:46.3333333+00:00

Dear Team!

With 31.03.2026, each subnet will be privated.

If I want to create a "AzureFirewallManagementSubnet" do I have to explictly enable the default outbound access or is it also working as a private subnet?

Here it is not mentioned, that I have to explicitly set "enable default outbound access". Please, clarify.

Azure Firewall
Azure Firewall

An Azure network security service that is used to protect Azure Virtual Network resources.

0 comments

Answer accepted by question author

Jose Benjamin Solis Nolasco 9,286 Reputation points Volunteer Moderator
2026-04-15T21:24:10.41+00:00

Hello Pittl Benedikt, Welcome to Microsoft Q&A

To directly answer your question: No, you do not need to explicitly enable default outbound access for the AzureFirewallManagementSubnet. It is fully supported and recommended to operate it as a private subnet (defaultOutboundAccess = false).

The March 31, 2026 retirement of Default Outbound Access (DOA) specifically targets Infrastructure-as-a-Service (IaaS) Virtual Machines that rely on implicit SNAT to reach the internet.

Azure Firewall, however, is a managed PaaS service. When you configure the AzureFirewallManagementSubnet (typically required for forced tunneling scenarios or Basic SKU firewalls), the firewall configuration strictly requires you to associate a dedicated Management Public IP address to it. Because the management traffic utilizes this explicit Public IP to communicate with the Azure control plane, it does not rely on or utilize the VM-style implicit "default outbound access" mechanism.

Therefore, setting the subnet to private has no negative impact on the Azure Firewall's ability to manage itself.

😊 If my answer helped you resolve your issue, please consider marking it as the correct answer. This helps others in the community find solutions more easily. Thanks!

Was this answer helpful?

1 person found this answer helpful.
0 comments

1 additional answer

Sort by: Most helpful
Most helpful Newest Oldest
  1. Vallepu Venkateswarlu 10,180 Reputation points Microsoft External Staff Moderator
    2026-04-15T21:20:59.78+00:00

    Hi Pittl Benedikt (INFRA.IT),

    Welcome to Microsoft Q&A Platform.

    The AzureFirewallManagementSubnet behaves just like any other subnet when it comes to default outbound access.

    Default change on March 31, 2026 : After that date, all new subnets in new VNets will be created as private by default (i.e. defaultOutboundAccess=false).

    The Azure portal already defaults subnets to private today, and ARM/CLI/PowerShell will follow suit with the newer API versions.

    What this means for your AzureFirewallManagementSubnet :

    • If you do nothing special, your management subnet will be private (no default outbound IP) after 3/31/2026.
    • The management-NIC documentation doesn’t call out “Enable default outbound” because it just inherits the subnet’s setting.

    Options for outbound connectivity on the management NIC a) Enable default outbound access on the subnet

    • In the portal, edit your management subnet and check Enable default outbound access—this flips defaultOutboundAccess=true an
    • Use an explicit outbound method (recommended for production), follow the How and when default outbound access is provided for more details

    Diagram of decision tree for default outbound access.
    If a Virtual Machine (VM) is deployed without an explicit outbound connectivity method, Azure assigns it a default outbound public IP address. This IP, known as the default outbound access IP, is owned by Microsoft and can change without notice. Additionally, default outbound connectivity relies on an implicit platform behavior and may be affected by platform‑level changes

    Reference list:

    Azure Firewall management NIC overview https://learn.microsoft.com/azure/firewall/management-nic

    Default outbound access in Azure (private subnets, disable/enable) https://learn.microsoft.com/azure/virtual-network/ip-services/default-outbound-access

    How to configure private subnets & toggle default outbound https://learn.microsoft.com/azure/virtual-network/ip-services/default-outbound-access#how-to-turn-off-default-outbound-access

    Attaching a NAT Gateway for explicit outbound https://learn.microsoft.com/azure/virtual-network/nat-gateway/overview

    Please210246-screenshot-2021-12-10-121802.pngand “up-vote” wherever the information provided helps you, this can be beneficial to other community members.

    Was this answer helpful?

    0 comments

Your answer

Answers can be marked as 'Accepted' by the question author and 'Recommended' by moderators, which helps users know the answer solved the author's problem.