Which statements about OSPF packets are true?

The statement that Hello packets are sent immediately after being added to an OSPF area is accurate because Hello packets are essential for OSPF operation. They are used for neighbor discovery and to maintain adjacency between OSPF routers. When a router joins an OSPF area, it must send Hello packets to establish communication with other routers in the same area. This process helps routers exchange information about their capabilities and reachability, ensuring they can connect and share routing information effectively.

The other statements present some inaccuracies regarding OSPF packet functions. For example, while a router does send LSAck packets after receiving an LSA Update, it is not the only action taken upon receiving such updates, and it is contextual based on the LSA processing state. LSA Update packets do carry detailed LSAs to synchronize the Link-State Database (LSDB), but they are not limited to this function and can occur at different times throughout the OSPF operation, not just during the adjacency establishment. Lastly, LSA Update packets are not restricted to the adjacency establishment phase; they can be sent during normal OSPF operation to convey routing changes and updates in the network topology.