What state does an OSPF router revert to if it is unable to receive Hello packets for a certain duration?

When an OSPF router is unable to receive Hello packets for a specified duration, it will revert to the Down state. In OSPF (Open Shortest Path First), Hello packets play a crucial role in discovering neighbors and maintaining neighbor relationships. These packets are sent at regular intervals to ensure that the nearby routers are still reachable and operational.

If a router stops receiving Hello packets from a neighbor, it indicates that the connection may be failing or that the neighboring router is down. After a set period, known as the dead interval, if no Hello packets are received, the router will conclude that it can no longer communicate with the neighbor and transitions to the Down state. This state signifies that the router is no longer able to reach the previously established neighbor, and subsequently, it will not use that router for path calculations.

The other states mentioned, such as Init and Loading, represent different points in the process of establishing or maintaining neighbor relationships but do not indicate a complete loss of connection. The 2-way state is part of the neighbor discovery process but does not represent a situation where there’s a failure to receive Hello packets.