Refer to the exhibit. Due to budget constraints, a customer decided to purchase WAN routers with one LAN and one WAN interface per device. There is a requirement to connect the three sites to ensure…

A dual-homed full mesh would require each router to have multiple WAN interfaces (at least two for full mesh connectivity and two for dual-homing) which contradicts the "one WAN interface per device" constraint.

A single-homed full mesh would require each router to establish logical connections to every other router in the mesh, which necessitates more than one logical connection over a single physical WAN interface, and more critically, a single physical interface router cannot directly connect point-to-point to two distinct peers simultaneously without a shared medium.

With the strict constraint of only one WAN interface per router, a single-homed hub-and-spoke design is the only physically viable option for connecting three sites. Each spoke router uses its single WAN interface to connect to the central hub, which also uses its single WAN interface to connect to the spokes (via logical tunnels over a shared WAN cloud), adhering to the interface limitation while providing connectivity.

A dual-homed hub-and-spoke design inherently requires at least two WAN interfaces per site/router to provide redundancy, which directly violates the "one WAN interface per device" limitation.