What happens after a router sends an OSPF Down State Hello packet?

After a router sends an OSPF Down State Hello packet, no OSPF neighbors are detected at that moment. In OSPF (Open Shortest Path First) operations, the Down State signifies that a router has yet to send or receive any Hello packets from its neighbors. When a router is in this state, it has not established any communication with neighboring routers, which means that it does not have any OSPF neighbors recognized. This situation prompts the router to try to discover neighbors by sending Hello packets.

While a router does not await acknowledgment from neighbors after sending a Down State Hello, nor does it check for its own router ID at this stage, it is critically important to note that the absence of detected neighbors leads the router into further attempts to establish OSPF adjacency. Transitioning directly to the Init State does occur, but only when a Hello packet has been sent and a response is received from a neighbor. Therefore, recognizing that no OSPF neighbors are detected at this point is vital, as it signifies the first step in establishing and monitoring OSPF neighbor relationships.