What is the first OSPF neighbor state?

In Open Shortest Path First (OSPF), the initial state of a neighbor relationship is known as the Down state. This is the state where OSPF has not yet detected any OSPF neighbors on the link. At this point, no Hello packets have been exchanged, and OSPF has not started the process of establishing a neighbor relationship.

When an OSPF router first powers on or connects to a network, it begins in the Down state. The router will then send Hello packets to discover and establish adjacencies with other OSPF routers. If a neighbor responds, the state transitions from Down to Init, indicating that a Hello packet has been received, but OSPF has not yet completed the process of establishing full communication with the neighbor.

Understanding these states is crucial for troubleshooting OSPF and ensuring proper OSPF operations within a network. The progression of states (Down to Init, then to other states like Exstart and Full) defines how neighbors are recognized and how routing tables are synchronized.