There are three types of OSPF exchanges:
1. Hello protocol exchange: This exchange happens when OSPF routers first come online or establish a neighbor relationship with each other. They exchange hello packets to establish and maintain the neighbor relationship.
1. Database Description (DBD) exchange: This exchange occurs when OSPF routers want to synchronize their link-state databases with each other. The routers exchange DBD packets that contain a summary of their link-state databases.
1. Link State Advertisement (LSA) exchange: This exchange takes place after the DBD exchange, and it involves the exchange of LSA packets. Routers use LSAs to update their databases with information about changes in the network topology.
