Connectivity architecture for Azure SQL Managed Instance

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Applies to: Azure SQL Managed Instance

This article describes the connectivity architecture in Azure SQL Managed Instance and how components direct communication traffic for a managed instance.

Overview

In SQL Managed Instance, an instance is placed inside the Azure virtual network and inside the subnet that's dedicated to managed instances. The deployment provides:

  • A secure virtual network-local (VNet-local) IP address.
  • The ability to connect an on-premises network to SQL Managed Instance.
  • The ability to connect SQL Managed Instance to a linked server or to another on-premises data store.
  • The ability to connect SQL Managed Instance to Azure resources.

High-level connectivity architecture

SQL Managed Instance is a set of service components that are hosted on a dedicated set of isolated virtual machines that are joined to a virtual cluster. Some service components are deployed inside the customer's virtual network subnet. Other services operate in a secure network environment that Azure manages.

Diagram that shows the high-level connectivity architecture for Azure SQL Managed Instance before November 2022.

Customer applications can connect to SQL Managed Instance and can query and update databases inside the virtual network, peered virtual network, or network connected by VPN or Azure ExpressRoute.

The following diagram shows entities that connect to SQL Managed Instance. It also shows the resources that need to communicate with a managed instance. The communication process at the bottom of the diagram represents customer applications and tools that connect to SQL Managed Instance as data sources.

Diagram that shows entities in the connectivity architecture for SQL Managed Instance before November 2022.

SQL Managed Instance is a single-tenant, platform as a service (PaaS) offering. Its compute and networking elements are deployed inside the customer's subnet. SQL Managed Instance typically is accessed via its VNet-local endpoint. SQL Managed Instance depends on Azure services like Azure Storage, Microsoft Entra ID, Azure Key Vault, Azure Event Hubs, and telemetry collection services. Traffic that originates in subnets that contain SQL Managed Instance might go to those services.

Deployment, management, and core service maintenance operations are carried out via automated agents. These agents have exclusive access to the compute resources that operate the service. You can't use ssh or Remote Desktop Protocol to access those hosts. All internal communications are encrypted and signed by using certificates. To check the trustworthiness of communicating parties, SQL Managed Instance constantly verifies these certificates by using certificate revocation lists.

Management endpoint

To facilitate communication between the control plane and the components deployed inside the customer's subnet, managed instances employ a management endpoint. This means that elements of the virtual network's infrastructure can harm management traffic by making the instance fail and become unavailable. Management and deployment services connect to SQL Managed Instance's management endpoint which is mapped to an external load balancer. Traffic is routed to the nodes only if it's received on a predefined set of ports that only the management components of SQL Managed Instance use. A built-in firewall on the nodes is set up to allow traffic only from Microsoft IP ranges. Certificates mutually authenticate all communication between management components and the management plane.

Note

Traffic that goes to Azure services that are inside the SQL Managed Instance region is optimized. Because the traffic is optimized, traffic isn't sent by Network Address Translation (NAT) to the public IP address for the management endpoint. If you need to use IP-based firewall rules, most commonly for storage, the service must be in a different region than SQL Managed Instance.

The Azure SQL Managed Instance mandatory inbound security rules require management ports 9000, 9003, 1438, 1440, and 1452 to be open from any source on the network security group (NSG) that protects SQL Managed Instance. Although these ports are open at the network security group level, they're protected at the network level by the built-in firewall.

The management endpoint is protected by a built-in firewall on the network level. On the application level, it's protected by mutual certificate verification. When connections start inside SQL Managed Instance, like in backups and audit logs, traffic appears to start from the management endpoint's public IP address.

Communication overview

Applications can connect to SQL Managed Instance via three types of endpoints. These endpoints serve different scenarios and exhibit distinct network properties and behaviors.

Diagram that shows the scope of visibility for VNet-local, public, and private endpoints to an Azure SQL Managed Instance.

VNet-local endpoint

The VNet-local endpoint is the default means to connect to SQL Managed Instance. The VNet-local endpoint is a domain name in the form of <mi_name>.<dns_zone>.database.chinacloudapi.cn that resolves to an IP address from the subnet's address pool; hence VNet-local, or an endpoint that is local to the virtual network. The VNet-local endpoint can be used to connect to a SQL Managed Instance in all standard connectivity scenarios.

VNet-local endpoints support the redirect connection type.

When connecting to the VNet-local endpoint, always use its domain name as the underlying IP address can occasionally change.

Public endpoint

The public endpoint is an optional domain name in the form of <mi_name>.public.<dns_zone>.database.chinacloudapi.cn that resolves to a public IP address reachable from the Internet. Public endpoint allows TDS traffic only to reach SQL Managed Instance on port 3342 and can't be used for integration scenarios, such as failover groups, Managed Instance link, and similar technologies.

When connecting to the public endpoint, always use its domain name as the underlying IP address can occasionally change.

Public endpoint always operates in proxy connection type.

Learn how to set up a public endpoint in Configure public endpoint for Azure SQL Managed Instance.

Private endpoints

A private endpoint is an optional fixed IP address in another virtual network that conducts traffic to your SQL managed instance. One Azure SQL Managed Instance can have multiple private endpoints in multiple virtual networks. Private endpoints allow TDS traffic only to reach SQL Managed Instance on port 1433 and can't be used for integration scenarios, such as failover groups, Managed Instance link, and other similar technologies.

When connecting to a private endpoint, always use the domain name since connecting to Azure SQL Managed Instance via its IP address isn't supported yet.

Private endpoints always operate in proxy connection type.

Learn more about private endpoints and how to configure them in Azure Private Link for Azure SQL Managed Instance.

Virtual cluster connectivity architecture

This section provides a closer look at the virtual cluster connectivity architecture of SQL Managed Instance. The following diagram shows the conceptual layout of the virtual cluster:

Diagram that shows the virtual cluster connectivity architecture for Azure SQL Managed Instance before November 2022.

The domain name of the VNet-local endpoint resolves to the private IP address of an internal load balancer. Although this domain name is registered in a public Domain Name System (DNS) zone and is publicly resolvable, its IP address belongs to the subnet's address range and can only be reached from inside its virtual network by default.

The load balancer directs traffic to a SQL Managed Instance gateway. Because multiple managed instances can run inside the same cluster, the gateway uses the SQL Managed Instance host name as seen in the connection string to redirect traffic to the correct SQL engine service.

The value for dns-zone is automatically generated when you create the cluster. If a newly created cluster hosts a secondary managed instance, it shares its zone ID with the primary cluster.

Service-aided subnet configuration

To improve service security, manageability, and availability, SQL Managed Instance applies a network intent policy on some elements of the Azure virtual network infrastructure. The policy configures the subnet, the associated network security group, and the route table to ensure that the minimum requirements for SQL Managed Instance are met. This platform mechanism transparently communicates networking requirements to users. The policy's main goal is to prevent network misconfiguration and to ensure normal SQL Managed Instance operations and service-level agreement commitment. When you delete a managed instance, the network intent policy is also removed.

A service-aided subnet configuration builds on top of the virtual network subnet delegation feature to provide automatic network configuration management.

Network requirements

The subnet in which SQL Managed Instance is deployed must have the following characteristics:

  • Dedicated subnet: The subnet SQL Managed Instance uses can be delegated only to the SQL Managed Instance service. The subnet can't be a gateway subnet, and you can deploy only SQL Managed Instance resources in the subnet.
  • Subnet delegation: The SQL Managed Instance subnet must be delegated to the Microsoft.Sql/managedInstances resource provider.
  • Network security group: A network security group must be associated with the SQL Managed Instance subnet. You can use a network security group to control access to the SQL Managed Instance data endpoint by filtering traffic on port 1433 and ports 11000-11999 when SQL Managed Instance is configured for redirect connections. The service automatically provisions rules and keeps them current as required to allow uninterrupted flow of management traffic.
  • Route table: A route table must be associated with the SQL Managed Instance subnet. You can add entries to this route table, for example to route traffic to premises through a virtual network gateway, or to add the default 0.0.0.0/0 route directing all traffic through a virtual network appliance such as a firewall. Azure SQL Managed Instance automatically provisions and manages its required entries in the route table.
  • Sufficient IP addresses: The SQL Managed Instance subnet must have at least 32 IP addresses. For more information, see Determine the size of the subnet for SQL Managed Instance. You can deploy managed instances in the existing network after you configure it to satisfy the networking requirements for SQL Managed Instance. Otherwise, create a new network and subnet.
  • Allowed by Azure policies: If you use Azure Policy to prevent resource creation or modification in a scope that includes a SQL Managed Instance subnet or virtual network, your policies must not prevent SQL Managed Instance from managing its internal resources. The following resources need to be excluded from policy deny effects for normal operation:
    • Resources of type Microsoft.Network/serviceEndpointPolicies, when resource name begins with \_e41f87a2\_
    • All resources of type Microsoft.Network/networkIntentPolicies
    • All resources of type Microsoft.Network/virtualNetworks/subnets/contextualServiceEndpointPolicies
  • Locks on virtual network: Locks on the dedicated subnet's virtual network, its parent resource group, or subscription, might occasionally interfere with SQL Managed Instance management and maintenance operations. Take special care when you use resource locks.
  • Replication traffic: Replication traffic for failover groups between two managed instances should be direct and not routed through a hub network.
  • Custom DNS server: If the virtual network is configured to use a custom DNS server, the DNS server must be able to resolve public DNS records. Using features like Microsoft Entra authentication might require resolving more fully qualified domain names (FQDNs). For more information, see Resolving private DNS names in Azure SQL Managed Instance.

Mandatory security rules with service-aided subnet configuration

To ensure inbound management traffic flow, the rules described in the following table are required:

Name Port Protocol Source Destination Action
management 9000, 9003, 1438, 1440, 1452 TCP SqlManagement MI SUBNET Allow
9000, 9003 TCP CorpnetSaw MI SUBNET Allow
9000, 9003 TCP CorpnetPublic MI SUBNET Allow
mi_subnet Any Any MI SUBNET MI SUBNET Allow
health_probe Any Any AzureLoadBalancer MI SUBNET Allow

To ensure outbound management traffic flow, the rules described in the following table are required:

Name Port Protocol Source Destination Action
management 443, 12000 TCP MI SUBNET AzureCloud Allow
mi_subnet Any Any MI SUBNET MI SUBNET Allow

Mandatory routes with service-aided subnet configuration

The routes that are described in the following table are necessary to ensure that management traffic is routed directly to a destination:

Name Address prefix Next hop 2
subnet-to-vnetlocal MI SUBNET 1 Virtual network
mi-azurecloud-REGION-internet AzureCloud.REGION Internet
mi-azurecloud-REGION_PAIR-internet AzureCloud.REGION_PAIR Internet
mi-azuremonitor-internet AzureMonitor Internet
mi-corpnetpublic-internet CorpNetPublic Internet
mi-corpnetsaw-internet CorpNetSaw Internet
mi-eventhub-REGION-internet EventHub.REGION Internet
mi-eventhub-REGION_PAIR-internet EventHub.REGION_PAIR Internet
mi-sqlmanagement-internet SqlManagement Internet
mi-storage-internet Storage Internet
mi-storage-REGION-internet Storage.REGION Internet
mi-storage-REGION_PAIR-internet Storage.REGION_PAIR Internet
mi-azureactivedirectory-internet AzureActiveDirectory Internet

Networking constraints

TLS 1.2 is enforced on outbound connections: Beginning in January 2020, Microsoft enforces TLS 1.2 for intra-service traffic in all Azure services. For SQL Managed Instance, this resulted in TLS 1.2 being enforced on outbound connections that are used for replication and on linked server connections to SQL Server. If you use a version of SQL Server that's earlier than 2016 with SQL Managed Instance, make sure that you apply TLS 1.2-specific updates.

The following virtual network features are currently not supported with SQL Managed Instance:

  • Microsoft peering: Enabling Microsoft peering on ExpressRoute circuits that are peered directly or transitively with a virtual network in which SQL Managed Instance resides affects traffic flow between SQL Managed Instance components inside the virtual network and services it depends on. Availability issues result. SQL Managed Instance deployments to a virtual network that already has Microsoft peering enabled are expected to fail.
  • Virtual network peering - global: Virtual network peering connectivity across Azure regions doesn't work for instances of SQL Managed Instance that are placed in subnets that were created before September 9, 2020.
  • Virtual network peering - configuration: When establishing virtual network peering between virtual networks that contain subnets with SQL Managed Instances, such subnets must use different route tables and network security groups (NSG). Reusing the route table and NSG in two or more subnets participating in virtual network peering will cause connectivity issues in all subnets using those route tables or NSG, and cause SQL Managed Instance's management operations to fail.
  • AzurePlatformDNS: Using the AzurePlatformDNS service tag to block platform DNS resolution would render SQL Managed Instance unavailable. Although SQL Managed Instance supports customer-defined DNS for DNS resolution inside the engine, there's a dependency on platform DNS for platform operations.
  • NAT gateway: Using Azure Virtual Network NAT to control outbound connectivity with a specific public IP address renders SQL Managed Instance unavailable. The SQL Managed Instance service is currently limited to use the basic load balancer, which doesn't provide coexistence of inbound and outbound flows with Azure Virtual Network NAT.
  • IPv6 for Azure Virtual Network: Deploying SQL Managed Instance to dual stack IPv4/IPv6 virtual networks is expected to fail. Associating a network security group or a route table with user-defined routes (UDRs) that contains IPv6 address prefixes to a SQL Managed Instance subnet renders SQL Managed Instance unavailable. Also, adding IPv6 address prefixes to a network security group or UDR that's already associated with a managed instance subnet renders SQL Managed Instance unavailable. SQL Managed Instance deployments to a subnet with a network security group and UDR that already have IPv6 prefixes are expected to fail.
  • Azure DNS private zones with a name reserved for Microsoft services: The following domain names are reserved names: chinacloudapi.cn, database.chinacloudapi.cn, core.chinacloudapi.cn, blob.core.chinacloudapi.cn, table.core.chinacloudapi.cn, management.core.chinacloudapi.cn, monitoring.core.chinacloudapi.cn, queue.core.chinacloudapi.cn, graph.chinacloudapi.cn, login.partner.microsoftonline.cn, login.chinacloudapi.cn, servicebus.chinacloudapi.cn, and vault.azure.cn. Deploying SQL Managed Instance to a virtual network that has an associated Azure DNS private zone that uses a name reserved for Microsoft services fails. Associating an Azure DNS private zone that uses a reserved name with a virtual network that contains a managed instance renders SQL Managed Instance unavailable. For information about Private Link configuration, see Azure Private Endpoint DNS configuration.

Next steps