What is the function of the Hello packet in OSPF?

The Hello packet in OSPF (Open Shortest Path First) serves the vital role of discovering and maintaining neighbor relationships between routers in the network. When OSPF routers start up, they send Hello packets to discover other OSPF routers on the same link. These packets contain essential information such as router priority, dead interval, and the router's OSPF process ID, which helps in establishing neighbor adjacency.

Once the Hello packets are exchanged, routers can recognize who their neighbors are, determine the state of those neighbors, and subsequently maintain those relationships. This is crucial for the stability and effectiveness of OSPF, as it operates on the principle of maintaining a consistent view of the network topology. If a router does not receive Hello packets from a neighbor within a specific interval, it can consider that neighbor down, thereby ensuring that only active and reachable routers are maintained in the routing table.

The other functions listed in the question, such as synchronizing routing tables or acknowledging received LSAs (Link State Advertisements), although important in the context of OSPF, are not performed by the Hello packet. Instead, they relate to other procedures in OSPF operations.