Final answer:
The OSPF routing protocol uses hello packets to verify active links between routers.
Step-by-step explanation:
The OSPF routing protocol uses hello packets to verify that a link between two routers is active and the routers are communicating. Hello packets are sent periodically by each OSPF router to establish and maintain neighbor relationships. When an OSPF router receives a hello packet from another router, it can determine if the link is active and functioning properly.