You have an Azure subscription that contains two instances of SQL Server on Azure Virtual Machines named VM1 and VM2. Both instances run Microsoft…

Deploying the virtual machines to different subnets creates a multi-subnet failover cluster. In a multi-subnet configuration, the cluster network name is assigned an IP address for each subnet. Only the IP address corresponding to the subnet of the active node is brought online. Client applications that use the MultiSubnetFailover=True connection string parameter can connect seamlessly after a failover. This architecture inherently handles traffic routing at the client driver level, thereby eliminating the need for an Azure Load Balancer or a Distributed Network Name (DNN) to direct traffic to the active node.

A. Proximity placement groups are used to reduce network latency between VMs but do not change the networking requirements for a failover cluster's virtual network name.

B. Using different proximity placement groups would increase latency and is not a recommended practice for a high-availability cluster; it does not address the networking requirement.

C. A single-subnet FCI on Azure VMs requires either an Azure Load Balancer or a Distributed Network Name (DNN) to route traffic to the active node's virtual IP.

1. Microsoft Docs

Cluster a SQL Server FCI on Azure VMs in multiple subnets. In the "Prerequisites" section

it states

"For a multi-subnet cluster

you don't need an Azure Load Balancer to route traffic to your FCI." This document details the procedure for creating an FCI that spans multiple subnets

which is the solution described in the correct answer.

2. Microsoft Docs

Failover cluster instances (FCI) with SQL Server on Azure VMs. Under the "Connectivity" section

it describes the traditional method using a Virtual Network Name (VNN) with an Azure Load Balancer and the newer method using a Distributed Network Name (DNN)

both of which are typically for single-subnet deployments. The multi-subnet approach is presented as an alternative that avoids both.

3. Microsoft Docs

MultiSubnetFailover for High Availability and Disaster Recovery. This document explains the client-side behavior: "Specify MultiSubnetFailover=True when connecting to a SQL Server availability group or a SQL Server Failover Cluster Instance. MultiSubnetFailover enables faster failover for all Availability Groups and Failover Cluster Instances in SQL Server...". This confirms how clients connect in a multi-subnet scenario without a load balancer.