Answer: One backup router
Step-by-step explanation:
A stub network is the type of the packet network that basically describe the computer notwork. It typically capable for sending the complex data in the single network path when the network aware about its destination.
A stub network contain the one backup router as the stub routing is the typically designed for conserve the resources of the local router like the central processing unit (CPU) and the memory. It basically improve the stability of the network in the system.