Your company has 40 branch offices that are linked by using a Software-Defined Wide Area Network (SD-WAN). The SD-WAN uses BGP. You have an Azure…

Azure Route Server is a fully managed service designed to simplify dynamic routing between a Network Virtual Appliance (NVA) and an Azure virtual network. In this scenario, the SD-WAN appliance in VNet1 is the NVA. By deploying Azure Route Server in the hub VNet (Vnet1), you can establish a BGP peering session between the Route Server and the NVA. The Route Server will then automatically learn the routes from the SD-WAN (advertised by the NVA) and propagate them to the route tables of all virtual networks in the hub-and-spoke topology. This eliminates the need to manually create and manage User-Defined Routes (UDRs), thus minimizing administrative effort as required.

A. An Azure VPN Gateway that has BGP enabled: A VPN Gateway is a distinct connectivity solution. The scenario already uses an NVA for connectivity; a VPN Gateway would be a parallel or replacement path, not a tool to integrate the existing NVA with the Azure fabric's routing.

B. a NAT gateway: A NAT gateway is used to provide outbound internet connectivity for virtual machines by translating private IP addresses to public ones. It does not participate in BGP or internal route propagation.

C. Azure Traffic Manager: This is a DNS-based traffic load balancer that operates at the application layer to distribute traffic to public endpoints. It is not involved in network-level BGP routing.

1. Microsoft Documentation - What is Azure Route Server?: "Azure Route Server simplifies dynamic routing between your network virtual appliance (NVA) and your virtual network. It allows you to exchange routing information directly through Border Gateway Protocol (BGP) routing protocol between any NVA that supports the BGP routing protocol and the Azure Software Defined Network (SDN) in the Azure Virtual Network (VNet) without the need to manually configure or maintain route tables."

Source: Microsoft Corporation. (2023). What is Azure Route Server?. Microsoft Learn. Retrieved from https://learn.microsoft.com/en-us/azure/route-server/overview (Section: "How does it work?")

2. Microsoft Documentation - Azure Route Server FAQ: "Do I need to configure User Defined Routes (UDRs) on my subnets to direct traffic to Azure Route Server? No. Azure Route Server only exchanges BGP routes with your NVA and propagates them to your VNet." This directly supports the "minimize administrative effort" requirement by eliminating manual UDR management.

Source: Microsoft Corporation. (2023). Azure Route Server FAQ. Microsoft Learn. Retrieved from https://learn.microsoft.com/en-us/azure/route-server/route-server-faq (Section: "Routing")

3. Microsoft Documentation - About BGP with Azure VPN Gateway: This document explains that BGP is used on the Azure VPN Gateway itself to exchange routes over IPsec S2S tunnels or ExpressRoute. It does not describe a mechanism for integrating a separate NVA's BGP routes into the VNet fabric.

Source: Microsoft Corporation. (2023). About BGP with Azure VPN Gateway. Microsoft Learn. Retrieved from https://learn.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-bgp-overview (Section: "Why use BGP?")