What is the neighbor status of OSPF? What is the reason if you stay in a certain state. (summary)

OSPF neighbor states are:

Down: No interaction.

init: The sender sends a HELLO packet waiting for a response.

Two-way: Linji relationship is established and DR/BDR elections are held.

exstart: pre-start, establish master-slave relationship, determine DBD package serial number.

exchange: Pre-interactive state, sending DBDs for local databases, and sending LSAs requesting updates they don't have.

loading: Database synchronization process, sending LSAs requesting updates it does not have.

FULL: Complete resume adjacency.

What is the reason for staying in a certain state?:

It stays in the init state because the sender sends a HELLO packet and the other party does not respond (the other party does not have a natwork segment).

Stay in two-way state for a long time, normal, DR/BDR election in progress, take a long time. But if it stays two-way, it's because both neighbors are DRO.

It stays in the exchange state because the MTUs of both parties are inconsistent.