What is the OSPF neighbor state if no Hello messages have been received?

In OSPF (Open Shortest Path First), the neighbor state indicates the status of the relationship between OSPF routers. If no Hello messages have been received from a neighboring router, the OSPF neighbor state will be categorized as "Down." This state reflects that the router has not established any communication with its potential neighbor.

The Down state occurs when a router has not yet detected another OSPF-enabled router on the link. Since OSPF relies heavily on Hello packets for discovering and maintaining neighbor relationships, the absence of these packets leads the router to assume that there are no active neighbors. A router in this state cannot proceed to exchange routing information or form a link-state database, which are critical functions for OSPF operation.

In contrast, other states like Init and 2-Way indicate that Hello messages have been exchanged but do not represent a lack of communication. Loading would imply that a neighbor adjacency is in the process of being established, which also does not apply in the absence of Hello messages. Thus, identifying the Down state appropriately reflects the condition of non-receipt of Hello messages.