Securing a custom VNET in Azure Container Apps with Network Security Groups

  • Article
  • 02/14/2025

Network Security Groups (NSGs) needed to configure virtual networks closely resemble the settings required by Kubernetes.

You can lock down a network via NSGs with more restrictive rules than the default NSG rules to control all inbound and outbound traffic for the Container Apps environment at the subscription level.

In the workload profiles environment, user-defined routes (UDRs) and securing outbound traffic with a firewall are supported. When using an external workload profiles environment, inbound traffic to Azure Container Apps is routed through the public IP that exists in the managed resource group rather than through your subnet. This means that locking down inbound traffic via NSG or Firewall on an external workload profiles environment isn't supported. For more information, see Networking in Azure Container Apps environments.

In the Consumption only environment, custom user-defined routes (UDRs) and ExpressRoutes aren't supported.

NSG allow rules

The following tables describe how to configure a collection of NSG allow rules. The specific rules required depend on your environment type.

Inbound

Protocol Source Source ports Destination Destination ports Description
TCP Your client IPs * Your container app's subnet1 80, 443 Allow your Client IPs to access Azure Container Apps. Use port 80 for HTTP and 443 for HTTPS.
TCP Your client IPs * The staticIP of your container app environment 80, 443 Allow your Client IPs to access Azure Container Apps. Use port 80 for HTTP and 443 for HTTPS.
TCP AzureLoadBalancer * Your container app's subnet 30000-327672 Allow Azure Load Balancer to probe backend pools.
TCP Your container app's subnet * Your container app's subnet * Required to allow the container app envoy sidecar to connect to envoy service.

1 This address is passed as a parameter when you create an environment. For example, 10.0.0.0/21.
2 The full range is required when creating your Azure Container Apps as a port within the range will by dynamically allocated. Once created, the required ports are two immutable, static values, and you can update your NSG rules.

Outbound

Note

When using Consumption only environments, all outbound ports required by Azure Kubernetes Service are also required for your container app.

Protocol Source Source ports Destination Destination ports Description
TCP Your container app's subnet * MicrosoftContainerRegistry 443 This is the service tag for Azure container registry for system containers.
TCP Your container app's subnet * AzureFrontDoor.FirstParty 443 This is a dependency of the MicrosoftContainerRegistry service tag.
UDP Your container app's subnet * AzureCloud.<REGION> 1194 Required for internal AKS secure connection between underlying nodes and control plane. Replace <REGION> with the region where your container app is deployed.
TCP Your container app's subnet * AzureCloud.<REGION> 9000 Required for internal AKS secure connection between underlying nodes and control plane. Replace <REGION> with the region where your container app is deployed.
TCP Your container app's subnet * AzureCloud 443 Allowing all outbound on port 443 provides a way to allow all FQDN based outbound dependencies that don't have a static IP.
UDP Your container app's subnet * * 123 NTP server.
Any Your container app's subnet * Your container app's subnet * Allow communication between IPs in your container app's subnet.
TCP and UDP Your container app's subnet * 168.63.129.16 53 Enables the environment to use Azure DNS to resolve the hostname.

Note: DNS communication to Azure DNS isn't subject to NSGs unless targeted using the AzurePlatformDNS service tag. To block DNS traffic, create an outbound rule to deny traffic to the AzurePlatformDNS service tag.
TCP Your container app's subnet1 * Your Container Registry Your container registry's port This is required to communicate with your container registry. For example, when using ACR, you need AzureContainerRegistry and AzureActiveDirectory for the destination, and the port is your container registry's port unless using private endpoints.2
TCP Your container app's subnet * Storage.<Region> 443 Only required when using Azure Container Registry to host your images.
TCP Your container app's subnet * AzureMonitor 443 Only required when using Azure Monitor. Allows outbound calls to Azure Monitor.

1 This address is passed as a parameter when you create an environment. For example, 10.0.0.0/21.
2 If you're using Azure Container Registry (ACR) with NSGs configured on your virtual network, create a private endpoint on your ACR to allow Azure Container Apps to pull images through the virtual network. You don't need to add an NSG rule for ACR when configured with private endpoints.

Considerations

  • If you're running HTTP servers, you might need to add ports 80 and 443.
  • Don't explicitly deny the Azure DNS address 168.63.129.16 in the outgoing NSG rules, or your Container Apps environment doesn't function.