An internal Azure Load Balancer is used to distribute traffic to resources inside a virtual network. To function, it requires a frontend IP configuration, which must be a private IP address allocated from the address space of a specific subnet within the virtual network. This private IP address serves as the destination for the traffic that the load balancer distributes. Other resources, like virtual machines or virtual machine scale sets, are then added to the backend pool of the load balancer.

B. storage account: A storage account itself does not reside in a subnet or consume an IP address from it. Connectivity can be enabled via a private endpoint, which is a network interface that gets an IP from the subnet, but the storage account resource is distinct.

C. service endpoints: A service endpoint is a feature enabled on a subnet to provide a direct, secure connection to Azure services over the Azure backbone. It does not consume any private IP addresses from the subnet's address range.

D. service endpoint policies: Service endpoint policies are applied to a subnet to filter egress traffic to specific Azure service instances over a service endpoint. They are a policy construct and do not require an IP address.

1. Microsoft Learn | Azure Load Balancer components: Under the "Frontend IP configuration" section

it states

"The IP address of your Azure Load Balancer. It's the point of contact for clients. ... For an internal load balancer

the frontend is a private IP address." This confirms the internal load balancer's frontend is an IP from the VNet.

2. Microsoft Learn | What is an internal load balancer?: In the "Frontend IP configuration" section

it details

"The private IP address is selected from a subnet of the virtual network where the load balancer is deployed." This explicitly links the required IP address to a subnet.

3. Microsoft Learn | Virtual Network service endpoints: In the "Key benefits" section

it clarifies that service endpoints allow VNet resources to connect to services without needing public IPs and that the connection is direct. It does not mention the consumption of private IPs by the endpoint itself.

4. Microsoft Learn | Use private endpoints for Azure Storage: This document explains

"A private endpoint is a network interface that uses a private IP address from your virtual network." This distinguishes the private endpoint (which gets an IP) from the storage account resource itself.