During OSPF neighbor adjacency formation, in which state is the initial database descriptor sequence number chosen?

In OSPF (Open Shortest Path First) neighbor adjacency formation, the initial database descriptor (DBD) sequence number is chosen during the ExStart state.

During the ExStart state, the OSPF routers decide which router will be the master and which will be the slave for the subsequent database exchange process. This state is crucial for establishing the parameters for the database exchange, including the sequence number that will be used in the subsequent Database Description packets. The choice of the sequence number signifies the beginning of the synchronization of databases between the neighboring routers and is essential for ensuring they exchange the correct and up-to-date routing information.

As the state transitions to the Exchange state, the routers use the chosen sequence number to send and acknowledge their DBD packets, facilitating the detailed exchange of routing information. Therefore, the ExStart state is critical for determining the manner in which OSPF routers will interact in the database synchronization process.