Deploy Azure Spring Apps in a virtual network

Note

The Basic, Standard, and Enterprise plans will be deprecated starting from mid-March, 2025, with a 3 year retirement period. We recommend transitioning to Azure Container Apps. For more information, see the Azure Spring Apps retirement announcement.

The Standard consumption and dedicated plan will be deprecated starting September 30, 2024, with a complete shutdown after six months. We recommend transitioning to Azure Container Apps. For more information, see Migrate Azure Spring Apps Standard consumption and dedicated plan to Azure Container Apps.

This article applies to: ✔️ Java ✔️ C#

This article applies to: ❌ Basic ✔️ Standard ✔️ Enterprise

This tutorial explains how to deploy an Azure Spring Apps instance in your virtual network. This deployment is sometimes called VNet injection.

The deployment enables:

• Isolation of Azure Spring Apps apps and service runtime from the internet on your corporate network.
• Azure Spring Apps interaction with systems in on-premises data centers or Azure services in other virtual networks.
• Empowerment of customers to control inbound and outbound network communications for Azure Spring Apps.

The following video describes how to secure Spring Boot applications using managed virtual networks.

Note

You can select your Azure virtual network only when you create a new Azure Spring Apps service instance. You can't change to use another virtual network after Azure Spring Apps has been created.

Prerequisites

Register the Azure Spring Apps resource provider Microsoft.AppPlatform and Microsoft.ContainerService according to the instructions in Register resource provider on Azure portal or by running the following Azure CLI command:

az provider register --namespace Microsoft.AppPlatform
az provider register --namespace Microsoft.ContainerService

Virtual network requirements

The virtual network to which you deploy your Azure Spring Apps instance must meet the following requirements:

• Location: The virtual network must reside in the same location as the Azure Spring Apps instance.
• Subscription: The virtual network must be in the same subscription as the Azure Spring Apps instance.
• Subnets: The virtual network must include two subnets dedicated to an Azure Spring Apps instance:
  • One for the service runtime.
  • One for your Spring applications.
  • There's a one-to-one relationship between these subnets and an Azure Spring Apps instance. Use a new subnet for each service instance you deploy. Each subnet can only include a single service instance.
• Address space: CIDR blocks up to /28 for both the service runtime subnet and the Spring applications subnet.
• Route table: By default the subnets don't need existing route tables associated. You can bring your own route table.

Use the following steps to set up the virtual network to contain the Azure Spring Apps instance.

Create a virtual network

Azure portal

If you already have a virtual network to host an Azure Spring Apps instance, skip steps 1, 2, and 3. You can start from step 4 to prepare subnets for the virtual network.

1. On the Azure portal menu, select Create a resource. From Azure Marketplace, select Networking > Virtual network.

2. In the Create virtual network dialog box, enter or select the following information:

   Setting	Value
   Subscription	Select your subscription.
   Resource group	Select your resource group, or create a new one.
   Name	Enter azure-spring-apps-vnet.
   Location	Select East US.

3. Select Next: IP Addresses.

4. For the IPv4 address space, enter 10.1.0.0/16.

5. Select Add subnet. Then enter service-runtime-subnet for Subnet name and enter 10.1.0.0/24 for Subnet address range. Then select Add.

6. Select Add subnet again, and then enter the subnet name and subnet address range. For example, enter apps-subnet and 10.1.1.0/24. Then select Add.

7. Select Review + create. Leave the rest as defaults, and select Create.

Azure CLI

If you already have a virtual network to host an Azure Spring Apps instance, skip steps 1, 2, 3 and 4. You can start from step 5 to prepare subnets for the virtual network.

1. Use the following command to define variables for your subscription, resource group, and Azure Spring Apps instance. Customize the values based on your real environment.

   export SUBSCRIPTION='<subscription-id>'
   export RESOURCE_GROUP='<resource-group-name>'
   export LOCATION='eastus'
   export AZURE_SPRING_APPS_INSTANCE_NAME='<Azure-Spring-Apps-Instance-name>'
   export VIRTUAL_NETWORK_NAME='azure-spring-apps-vnet'
   

2. Use the following command to sign in to the Azure CLI and choose your active subscription.

   az login
   az account set --subscription ${SUBSCRIPTION}
   

3. Use the following command to create a resource group for your resources:

   az group create --name $RESOURCE_GROUP --location $LOCATION
   

4. Use the following command to create the virtual network:

   az network vnet create \
       --resource-group $RESOURCE_GROUP \
       --name $VIRTUAL_NETWORK_NAME \
       --location $LOCATION \
       --address-prefix 10.1.0.0/16
   

5. Use the following command to create two subnets in this virtual network:

   az network vnet subnet create \
       --resource-group $RESOURCE_GROUP \
       --vnet-name $VIRTUAL_NETWORK_NAME \
       --address-prefixes 10.1.0.0/24 \
       --name service-runtime-subnet
   az network vnet subnet create \
       --resource-group $RESOURCE_GROUP \
       --vnet-name $VIRTUAL_NETWORK_NAME \
       --address-prefixes 10.1.1.0/24 \
       --name apps-subnet
   

Grant service permission to the virtual network

This section shows you how to grant Azure Spring Apps the User Access Administrator and Network Contributor permissions on your virtual network. This permission enables you to grant a dedicated and dynamic service principal on the virtual network for further deployment and maintenance.

Note

If you're using your own route table or a user defined route feature, you also need to grant Azure Spring Apps the same role assignments to your route tables. For more information, see the Bring your own route table section and Control egress traffic for an Azure Spring Apps instance.

Azure portal

Use the following steps to grant permission:

1. Select the virtual network azure-spring-apps-vnet you previously created.

2. Select Access control (IAM), and then select Add > Add role assignment.

   

3. Assign the Network Contributor and User Access Administrator roles to the Azure Spring Cloud Resource Provider. For more information, see Assign Azure roles using the Azure portal.

   Note

   Role User Access Administrator is in the Privileged administrator roles and Network Contributor is in the Job function roles.

Azure CLI

Use the following commands to grant permission:

export VIRTUAL_NETWORK_RESOURCE_ID=$(az network vnet show \
    --resource-group $RESOURCE_GROUP \
    --name $VIRTUAL_NETWORK_NAME \
    --query "id" \
    --output tsv)

az role assignment create \
    --role "User Access Administrator" \
    --scope ${VIRTUAL_NETWORK_RESOURCE_ID} \
    --assignee e8de9221-a19c-4c81-b814-fd37c6caf9d2

az role assignment create \
    --role "Network Contributor" \
    --scope ${VIRTUAL_NETWORK_RESOURCE_ID} \
    --assignee e8de9221-a19c-4c81-b814-fd37c6caf9d2

The --assignee argument represents the service principal Azure Spring Apps uses to interact with the customer's virtual network.

Deploy an Azure Spring Apps instance

Azure portal

Use the following steps to deploy an Azure Spring Apps instance in the virtual network:

1. Open the Azure portal.

2. In the top search box, search for Azure Spring Apps. Select Azure Spring Apps from the result.

3. On the Azure Spring Apps page, select Add.

4. Fill out the form on the Azure Spring Apps Create page.

5. Select the same resource group and region as the virtual network.

6. For Name under Service Details, select azure-spring-apps-vnet.

7. Select the Networking tab, and select the following values:

   Setting	Value
   Deploy in your own virtual network	Select Yes.
   Virtual network	Select azure-spring-apps-vnet.
   Service runtime subnet	Select service-runtime-subnet.
   Spring Boot microservice apps subnet	Select apps-subnet.

   

8. Select Review and create.

9. Verify your specifications, and select Create.

   

Azure CLI

To deploy an Azure Spring Apps instance in the virtual network:

Use the following command to create your Azure Spring Apps instance, specifying the virtual network and subnets you created previously:

az spring create  \
    --resource-group "$RESOURCE_GROUP" \
    --name "$AZURE_SPRING_APPS_INSTANCE_NAME" \
    --vnet $VIRTUAL_NETWORK_NAME \
    --service-runtime-subnet service-runtime-subnet \
    --app-subnet apps-subnet \
    --enable-java-agent \
    --sku standard \
    --location $LOCATION

After the deployment, two more resource groups are created in your subscription to host the network resources for the Azure Spring Apps instance. Go to Home, and then select Resource groups from the top menu items to find the following new resource groups.

The resource group named as ap-svc-rt_{service instance name}_{service instance region} contains network resources for the service runtime of the service instance.

The resource group named as ap-app_{service instance name}_{service instance region} contains network resources for your Spring applications of the service instance.

Those network resources are connected to your virtual network created in the preceding image.

Important

The resource groups are fully managed by the Azure Spring Apps service. Do not manually delete or modify any resource inside.

Using smaller subnet ranges

This table shows the maximum number of app instances Azure Spring Apps supports using smaller subnet ranges.

App subnet CIDR	Total IPs	Available IPs	Maximum app instances
/28	16	8	App with 0.5 core: 192 App with one core: 96 App with two cores: 48 App with three cores: 32 App with four cores: 24
/27	32	24	App with 0.5 core: 456 App with one core: 228 App with two cores: 144 App with three cores: 96 App with four cores: 72
/26	64	56	App with 0.5 core: 500 App with one core: 500 App with two cores: 336 App with three cores: 224 App with four cores: 168
/25	128	120	App with 0.5 core: 500 App with one core: 500 App with two cores: 500 App with three cores: 480 App with four cores: 360
/24	256	248	App with 0.5 core: 500 App with one core: 500 App with two cores: 500 App with three cores: 500 App with four cores: 500

For subnets, Azure reserves five IP addresses, and Azure Spring Apps requires at least three IP addresses. At least eight IP addresses are required, so /29 and /30 are nonoperational.

For a service runtime subnet, the minimum size is /28.

Note

A small subnet range impacts the underlying resource you can use for system components like ingress controller. Azure Spring Apps uses an underlying ingress controller to handle application traffic management. The number of ingress controller instances automatically increases as application traffic increases. Reserve a larger virtual network subnet IP range if application traffic could increase in the future. You typically reserve one IP addresses for traffic of 10000 requests per second.

Bring your own route table

Azure Spring Apps supports using existing subnets and route tables.

If your custom subnets don't contain route tables, Azure Spring Apps creates them for each of the subnets and adds rules to them throughout the instance lifecycle. If your custom subnets contain route tables, Azure Spring Apps acknowledges the existing route tables during instance operations and adds/updates and/or rules accordingly for operations.

Warning

Custom rules can be added to the custom route tables and updated. However, rules are added by Azure Spring Apps and these must not be updated or removed. Rules such as 0.0.0.0/0 must always exist on a given route table and map to the target of your internet gateway, such as an NVA or other egress gateway. Use caution when updating rules when only your custom rules are being modified.

Route table requirements

The route tables to which your custom virtual network is associated must meet the following requirements:

• You can associate your Azure route tables with your virtual network only when you create a new Azure Spring Apps service instance. You can't change to use another route table after you create an Azure Spring Apps instance.
• Both the Spring application subnet and the service runtime subnet must associate with different route tables or neither of them.
• Permissions must be assigned before instance creation. Be sure to grant Azure Spring Cloud Resource Provider the User Access Administrator and Network Contributor permissions on your route tables.
• You can't update the associated route table resource after cluster creation. While you can't update the route table resource, you can modify custom rules on the route table.
• You can't reuse a route table with multiple instances due to potential conflicting routing rules.

Using Custom DNS Servers

Azure Spring Apps supports using custom DNS servers in your virtual network.

If you don't specify custom DNS servers in your DNS Server Virtual Network setting, Azure Spring Apps will, by default, use the Azure DNS to resolve IP addresses. If your virtual network is configured with custom DNS settings, add Azure DNS IP 168.63.129.16 as the upstream DNS server in the custom DNS server. Azure DNS can resolve IP addresses for all the public FQDNs mentioned in Customer responsibilities running Azure Spring Apps in a virtual network. It can also resolve IP address for *.svc.private.azuremicroservices.io in your virtual network.

If your custom DNS server can't add Azure DNS IP 168.63.129.16 as the upstream DNS server, use the following steps:

• Ensure that your custom DNS server can resolve IP addresses for all the public FQDNs. For more information, see Customer responsibilities running Azure Spring Apps in a virtual network.
• Add the DNS record *.svc.private.azuremicroservices.io to the IP of your application. For more information, see the Find the IP address for your application section of Access an app in Azure Spring Apps in a virtual network.

Next steps

• Troubleshooting Azure Spring Apps in virtual networks
• Customer responsibilities for Running Azure Spring Apps in a virtual network