Fabrikam has a hub-and-spoke design. The hub contains an Azure Route Server and an NVA. One on-prem branch connects via an ExpressRoute circuit to the hub and another branch connects via a Site-to-Site VPN to the same hub. Fabrikam wants branch-to-branch connectivity (traffic between the two on-prem branches) to be routed through Azure without hairpinning back to a colo. Which statement accurately describes a limitation and the recommended approach for enabling branch-to-branch routing in this scenario?

The correct answer states that Azure Route Server cannot directly peer with Azure virtual network gateways (VPN or ExpressRoute). This is a fundamental limitation. To achieve branch-to-branch connectivity through Azure in this scenario, the NVA must act as the central route exchange point. The NVA peers with the Azure Route Server, which then learns routes from the NVA. The NVA is also responsible for establishing BGP sessions with both the VPN Gateway and the ExpressRoute gateway (or receiving routes from on-premises devices through these gateways) and redistributing routes between them. This ensures that the NVA has visibility into both branch networks and can advertise them to the Azure Route Server, enabling end-to-end routing. The first incorrect option is wrong because Azure Route Server does not directly peer with Azure virtual network gateways. The third option is incorrect as deploying a second Route Server doesn't overcome the peering limitation with gateways and would add unnecessary complexity. The fourth option is impractical and unnecessary; converting ExpressRoute to VPN would degrade performance and doesn't address the core routing challenge with mixed gateway types.