You have 10 on-premises sites connected with a third‑party SD‑WAN solution and five Azure virtual networks. You plan to connect the Azure virtual networks and on-premises networks using a single Azure Virtual WAN hub. To allow the Azure Virtual WAN hub to act as a node within the third‑party SD‑WAN fabric, what should you deploy?

A Network Virtual Appliance (NVA) is the correct choice because it allows the Azure Virtual WAN hub to integrate directly with a third-party SD-WAN solution. An NVA, such as a virtual firewall or a virtual router, can be deployed within the Virtual WAN hub to provide the necessary routing and networking capabilities to act as a node in the SD-WAN fabric. This enables the SD-WAN solution to manage traffic flow between on-premises sites and Azure virtual networks through the Virtual WAN hub. An ExpressRoute gateway is for connecting on-premises networks to Azure via a private, dedicated connection, not for integrating with a third-party SD-WAN fabric. Site-to-site and Point-to-site gateways are VPN solutions primarily for connecting individual sites or users to Azure, respectively, and do not provide the advanced integration capabilities required for a third-party SD-WAN fabric.