Final answer:
The most common topology for DMVPN is hub and spoke, which is favored for its scalability and reduced complexity when adding new spokes, as they only need to connect to the hub.option d is true.
Step-by-step explanation:
The most common topology seen with a DMVPN (Dynamic Multipoint Virtual Private Network) is hub and spoke, also known as partial mesh. This topology consists of a central hub that acts as a point of concentration for spokes, which are the remote sites. In a DMVPN network, the hub maintains a VPN tunnel with each spoke. This allows for direct communication between spokes through the hub, without the need for a permanent VPN connection between every pair of spokes, which you would see in a full mesh topology.
The hub and spoke design of DMVPN simplifies the scalability of the network. When a new spoke is added, it only needs to establish a connection with the hub, not with every other spoke. This greatly reduces the complexity and configuration requirements as the network grows.