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Connect to a virtual network in internal mode using Azure API Management

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With Azure virtual networks (VNets), Azure API Management can manage internet-inaccessible APIs using several VPN technologies to make the connection. For VNet connectivity options, requirements, and considerations, see Using a virtual network with Azure API Management.

This article explains how to set up VNet connectivity for your API Management instance in the internal mode. In this mode, you can only access the following API Management endpoints within a VNet whose access you control.

  • The API gateway
  • The developer portal
  • Direct management
  • Git

Note

  • None of the API Management endpoints are registered on the public DNS. The endpoints remain inaccessible until you configure DNS for the VNet.
  • To use the self-hosted gateway in this mode, also enable private connectivity to the self-hosted gateway configuration endpoint. Currently, API Management doesn't enable configuring a custom domain name for the v2 endpoint.

Use API Management in internal mode to:

  • Make APIs hosted in your private datacenter securely accessible by third parties outside of it by using Azure VPN connections or Azure ExpressRoute.
  • Enable hybrid cloud scenarios by exposing your cloud-based APIs and on-premises APIs through a common gateway.
  • Manage your APIs hosted in multiple geographic locations, using a single gateway endpoint.

Connect to internal VNet

For configurations specific to the external mode, where the API Management endpoints are accessible from the public internet, and backend services are located in the network, see Connect to a virtual network using Azure API Management.

Note

We recommend that you use the Azure Az PowerShell module to interact with Azure. See Install Azure PowerShell to get started. To learn how to migrate to the Az PowerShell module, see Migrate Azure PowerShell from AzureRM to Az.

Availability

Important

This feature is available in the Premium and Developer tiers of API Management.

Prerequisites

Some prerequisites differ depending on the version (stv2 or stv1) of the compute platform hosting your API Management instance.

Tip

When you use the portal to create or update the network connection of an existing API Management instance, the instance is hosted on the stv2 compute platform.

  • A virtual network and subnet in the same region and subscription as your API Management instance.

    • The subnet used to connect to the API Management instance may contain other Azure resource types.
    • The subnet shouldn't have any delegations enabled. The Delegate subnet to a service setting for the subnet should be set to None.

  • A network security group attached to the subnet above. A network security group (NSG) is required to explicitly allow inbound connectivity, because the load balancer used internally by API Management is secure by default and rejects all inbound traffic. For specific configuration, see Configure NSG rules, later in this article.

  • A Standard SKU public IPv4 address. The public IP address resource is required when setting up the virtual network for either external or internal access. With an internal virtual network, the public IP address is used only for management operations. Learn more about IP addresses of API Management.

    • The IP address must be in the same region and subscription as the API Management instance and the virtual network.

    • When creating a public IP address resource, ensure you assign a DNS name label to it. The label you choose to use does not matter but a label is required if this resource will be assigned to an API Management service.

    • For best network performance, it's recommended to use the default Routing preference: Microsoft network.

    • When creating a public IP address in a region where you plan to enable zone redundancy for your API Management instance, configure the Zone-redundant setting.

    • The value of the IP address is assigned as the virtual public IPv4 address of the API Management instance in that region.

    • When changing from an external to internal virtual network (or vice versa), changing subnets in the network, or updating availability zones for the API Management instance, you must configure a different public IP address.

Enable VNet connection

Enable VNet connectivity using the Azure portal (stv2 platform)

  1. Go to the Azure portal to find your API management instance. Search for and select API Management services.

  2. Choose your API Management instance.

  3. Select Network > Virtual network.

  4. Select the Internal access type.

  5. In the list of locations (regions) where your API Management service is provisioned:

    1. Choose a Location.
    2. Select Virtual network, Subnet, and IP address.
      • The VNet list is populated with Resource Manager VNets available in your Azure subscriptions, set up in the region you are configuring.

  6. Select Apply. The Virtual network page of your API Management instance is updated with your new VNet and subnet choices. Set up internal VNet in Azure portal

  7. Continue configuring VNet settings for the remaining locations of your API Management instance.

  8. In the top navigation bar, select Save, then select Apply network configuration.

    It can take 15 to 45 minutes to update the API Management instance. The Developer tier has downtime during the process. The Basic and higher SKUs don't have downtime during the process.

After successful deployment, you should see your API Management service's private virtual IP address and public virtual IP address on the Overview blade. For more information about the IP addresses, see Routing in this article.

Public and private IP addressed in Azure portal

Note

Since the gateway URL is not registered on the public DNS, the test console available on the Azure portal will not work for an internal VNet deployed service. Instead, use the test console provided on the developer portal.

Enable connectivity using a Resource Manager template (stv2 platform)

  • Azure Resource Manager template (API version 2021-08-01 )

    Deploy to Azure

Enable connectivity using Azure PowerShell cmdlets (stv1 platform)

Create or update an API Management instance in a VNet.

Configure NSG rules

Configure custom network rules in the API Management subnet to filter traffic to and from your API Management instance. We recommend the following minimum NSG rules to ensure proper operation and access to your instance.

Important

Depending on your use of monitoring and other features, you may need to configure additional NSG rules beyond the minimum rules in the following table. For detailed settings, see Virtual network configuration reference.

  • For most scenarios, use the indicated service tags instead of service IP addresses to specify network sources and destinations.
  • Set the priority of these rules higher than that of the default rules.
Source / Destination Port(s) Direction Transport protocol Service tags
Source / Destination		 Purpose VNet type
* / [80], 443 Inbound TCP Internet / VirtualNetwork Client communication to API Management External only
* / 3443 Inbound TCP ApiManagement / VirtualNetwork Management endpoint for Azure portal and PowerShell External & Internal
* / 6390 Inbound TCP AzureLoadBalancer / VirtualNetwork Azure Infrastructure Load Balancer External & Internal
* / 443 Outbound TCP VirtualNetwork / Storage Dependency on Azure Storage External & Internal
* / 1433 Outbound TCP VirtualNetwork / SQL Access to Azure SQL endpoints External & Internal
* / 443 Outbound TCP VirtualNetwork / AzureKeyVault Access to Azure Key Vault External & Internal

DNS configuration

In internal VNet mode, you have to manage your own DNS to enable inbound access to your API Management endpoints.

We recommend:

  1. Configure an Azure DNS private zone.
  2. Link the Azure DNS private zone to the VNet into which you've deployed your API Management service.

Learn how to set up a private zone in Azure DNS.

Note

The API Management service does not listen to requests on its IP addresses. It only responds to requests to the host name configured on its endpoints. These endpoints include:

  • API gateway
  • The Azure portal
  • The developer portal
  • Direct management endpoint
  • Git

Access on default host names

When you create an API Management service (contosointernalvnet, for example), the following endpoints are configured by default:

Endpoint Endpoint configuration
API Gateway contosointernalvnet.azure-api.net
Developer portal contosointernalvnet.portal.azure-api.net
The new developer portal contosointernalvnet.developer.azure-api.net
Direct management endpoint contosointernalvnet.management.azure-api.net
Git contosointernalvnet.scm.azure-api.net

To access these API Management endpoints, you can create a virtual machine in a subnet connected to the VNet in which API Management is deployed. Assuming the private virtual IP address for your service is 10.1.0.5, you can map the hosts file as follows. The hosts mapping file is at %SystemDrive%\drivers\etc\hosts (Windows) or /etc/hosts (Linux, macOS).

Internal virtual IP address Endpoint configuration
10.1.0.5 contosointernalvnet.azure-api.net
10.1.0.5 contosointernalvnet.portal.azure-api.net
10.1.0.5 contosointernalvnet.developer.azure-api.net
10.1.0.5 contosointernalvnet.management.azure-api.net
10.1.0.5 contosointernalvnet.scm.azure-api.net

You can then access all the API Management endpoints from the virtual machine you created.

Access on custom domain names

If you don't want to access the API Management service with the default host names:

  1. Set up custom domain names for all your endpoints, as shown in the following image:

    Set up custom domain name

  2. Create records in your DNS server to access the endpoints accessible from within your VNet. Map the endpoint records to the private virtual IP address for your service.

Routing

The following virtual IP addresses are configured for an API Management instance in an internal virtual network.

Virtual IP address Description
Private virtual IP address A load balanced IP address from within the API Management instance's subnet range (DIP), over which you can access the API gateway, developer portal, management, and Git endpoints.

Register this address with the DNS servers used by the VNet.
Public virtual IP address Used only for control plane traffic to the management endpoint over port 3443. Can be locked down to the ApiManagement service tag.

The load-balanced public and private IP addresses can be found on the Overview blade in the Azure portal.

For more information and considerations, see IP addresses of Azure API Management.

VIP and DIP addresses

Dynamic IP (DIP) addresses will be assigned to each underlying virtual machine in the service and used to access endpoints and resources in the VNet and in peered VNets. The API Management service's public virtual IP (VIP) address will be used to access public-facing resources.

If IP restriction lists secure resources within the VNet or peered VNets, we recommend specifying the entire subnet range where the API Management service is deployed to grant or restrict access from the service.

Learn more about the recommended subnet size.

Example

If you deploy 1 capacity unit of API Management in the Premium tier in an internal VNet, 3 IP addresses will be used: 1 for the private VIP and one each for the DIPs for two VMs. If you scale out to 4 units, more IPs will be consumed for additional DIPs from the subnet.

If the destination endpoint has allow-listed only a fixed set of DIPs, connection failures will result if you add new units in the future. For this reason and since the subnet is entirely in your control, we recommend allow-listing the entire subnet in the backend.

Force tunnel traffic to on-premises firewall using ExpressRoute or network virtual appliance

Forced tunneling lets you redirect or "force" all internet-bound traffic from your subnet back to on-premises for inspection and auditing. Commonly, you configure and define your own default route (0.0.0.0/0), forcing all traffic from the API Management subnet to flow through an on-premises firewall or to a network virtual appliance. This traffic flow breaks connectivity with API Management, since outbound traffic is either blocked on-premises, or NAT'd to an unrecognizable set of addresses that no longer work with various Azure endpoints. You can solve this issue via the following methods:

  • Enable service endpoints on the subnet in which the API Management service is deployed for:

    • Azure SQL (required only in the primary region if the API Management service is deployed to multiple regions)
    • Azure Storage
    • Azure Event Hubs
    • Azure Key Vault (required when API Management is deployed on the stv2 platform)

    By enabling endpoints directly from the API Management subnet to these services, you can use the Microsoft Azure backbone network, providing optimal routing for service traffic. If you use service endpoints with a force tunneled API Management, traffic for the preceding Azure services isn't force tunneled. However, the other API Management service dependency traffic remains force tunneled. Ensure that your firewall or virtual appliance doesn't block this traffic, or the API Management service may not function properly.

    Note

    We strongly recommend enabling service endpoints directly from the API Management subnet to dependent services such as Azure SQL and Azure Storage that support them. However, some organizations may have requirements to force tunnel all traffic from the API Management subnet. In this case, ensure that you configure your firewall or virtual appliance to allow this traffic. You will need to allow the complete IP address range of each dependent service, and keep this configuration up to date when the Azure infrastructure changes. Your API Management service may also experience latency or unexpected timeouts because of the force tunneling of this network traffic.

  • All the control plane traffic from the internet to the management endpoint of your API Management service is routed through a specific set of inbound IPs, hosted by API Management. When the traffic is force tunneled, the responses won't symmetrically map back to these inbound source IPs and connectivity to the management endpoint is lost. To overcome this limitation, configure user-defined routes (UDRs) for these inbound IPs with next hop type set to "Internet", to steer traffic back to Azure. Configure the ApiManagement service tag, or find the set of inbound IPs for control plane traffic documented in Control plane IP addresses.

    Important

    Control plane IP addresses should be configured for network access rules and routes only when needed in certain networking scenarios. We recommend using the ApiManagement service tag instead of control plane IP addresses to prevent downtime when infrastructure improvements necessitate IP address changes.

    Note

    Allowing API Management management traffic to bypass an on-premises firewall or network virtual appliance isn't considered a significant security risk. The recommended configuration for your API Management subnet allows inbound management traffic on port 3443 only from the set of Azure IP addresses encompassed by the ApiManagement service tag. The recommended UDR configuration is only for the return path of this Azure traffic.

  • (External VNet mode) Data plane traffic for clients attempting to reach the API Management gateway and developer portal from the internet will also be dropped by default because of asymmetric routing introduced by forced tunneling. For each client that requires access, configure an explicit UDR with next hop type "Internet" to bypass the firewall or virtual network appliance.

  • For other force tunneled API Management service dependencies, resolve the hostname and reach out to the endpoint. These include:

    • Metrics and Health Monitoring
    • Azure portal diagnostics
    • SMTP relay
    • Developer portal CAPTCHA
    • Azure KMS server

For more information, see Virtual network configuration reference.

Common network configuration issues

This section has moved. See Virtual network configuration reference.

Troubleshooting

  • Unsuccessful initial deployment of API Management service into a subnet

    • Deploy a virtual machine into the same subnet.
    • Connect to the virtual machine and validate connectivity to one of each of the following resources in your Azure subscription:
      • Azure Storage blob
      • Azure SQL Database
      • Azure Storage Table
      • Azure Key Vault (for an API Management instance hosted on the stv2 platform)

    Important

    After validating the connectivity, remove all the resources in the subnet before deploying API Management into the subnet (required when API Management is hosted on the stv1 platform).

  • Verify network status

    • After deploying API Management into the subnet, use the portal to check the connectivity of your instance to dependencies, such as Azure Storage.
    • In the portal, in the left-hand menu, under Deployment and infrastructure, select Network > Network status.

    Verify network connectivity status in the portal

    Filter Description
    Required Select to review the required Azure services connectivity for API Management. Failure indicates that the instance is unable to perform core operations to manage APIs.
    Optional Select to review the optional services connectivity. Failure indicates only that the specific functionality will not work (for example, SMTP). Failure may lead to degradation in using and monitoring the API Management instance and providing the committed SLA.

    To address connectivity issues, review network configuration settings and fix required network settings.

  • Incremental updates
    When making changes to your network, refer to NetworkStatus API to verify that the API Management service has not lost access to critical resources. The connectivity status should be updated every 15 minutes.

    To apply a network configuration change to the API Management instance using the portal:

    1. In the left-hand menu for your instance, under Deployment and infrastructure, select Virtual network.
    2. Select Apply network configuration.

  • Resource navigation links
    An APIM instance hosted on the stv1 compute platform, when deployed into a Resource Manager VNET subnet, reserves the subnet by creating a resource navigation link. If the subnet already contains a resource from a different provider, deployment will fail. Similarly, when you delete an API Management service, or move it to a different subnet, the resource navigation link will be removed.

  • Challenges encountered in reassigning APIM instance to previous subnet

    • When moving an APIM instance back to its original subnet, immediate reassignment may not be possible due to the VNET lock, which takes up to six hours to be removed. If the original subnet has other APIM services (cloud service-based), deleting them and waiting for 6 hours is necessary for deploying a VMSS-based service in the same subnet.
    • Another scenario to consider is the presence of a scope lock at the resource group level or higher, hindering the Resource Navigation Link Deletion process. To resolve this, remove the scope lock and allow a delay of approximately 4-6 hours for the APIM service to unlink from the original subnet before the lock removal, enabling deployment to the desired subnet.

Next steps

Learn more about: