You have an on-premises network that is connected to an Azure virtual network by using a Site-to- Site VPN. Each network contains a subnet that has…

Azure Extended Network is a feature designed specifically to stretch an on-premises subnet into Azure. This creates a Layer 2 network extension, allowing on-premises virtual machines to be migrated to Azure while retaining their original private IP addresses. This is crucial for scenarios where applications are hard-coded with IP addresses or when re-IPing is not feasible. The feature directly addresses the core requirements of the question: migrating a VM to an overlapping subnet in Azure without changing its IP address and with minimal administrative effort, as it avoids any network reconfiguration on the migrated VM.

B. Azure Virtual Network NAT: This service simplifies outbound-only internet connectivity for virtual networks. It does not facilitate network extension from on-premises or resolve overlapping IP address space issues for migration.

C. Azure Application Gateway: This is a Layer 7 web traffic load balancer. It manages HTTP/S traffic to web applications and is not designed for Layer 2/3 network extension or VM migration.

D. Azure virtual network peering: This connects two Azure virtual networks. A fundamental requirement for VNet peering is that the connected networks must have non-overlapping IP address spaces, which contradicts the scenario described.

1. Microsoft Learn

Azure Extended Network for Windows Admin Center. This document explicitly states

"Extended network is a feature that allows you to stretch an on-premises subnet to Azure to allow on-premises virtual machines to keep their original on-premises private IP addresses when migrating to Azure."

Source: Microsoft Learn. Section: "Overview of Azure Extended Network for Windows Admin Center".

2. Microsoft Learn

What is Virtual Network NAT? This document defines the purpose of VNet NAT. "Virtual Network NAT (network address translation) simplifies outbound-only internet connectivity for virtual networks... With a NAT gateway

VMs without public IP addresses can connect to the internet."

Source: Microsoft Learn. Section: "What is Virtual Network NAT?".

3. Microsoft Learn

Azure virtual network peering. This document outlines the constraints of VNet peering. "The virtual networks you peer must have non-overlapping IP address spaces."

Source: Microsoft Learn. Section: "Virtual network peering - Requirements and constraints".