The various states in which a neighbor can be are discussed below.
1. Down - the initial state of a neighbor conversation.
2. Attempt - indicates that an attempt should be made to contact the neighbor.
3. Init - hello packet has been received from the neighbor.
4. 2-Way - communication between two routers is bi-directional.
5. ExStart - first step to creating an adjacency between the two neighboring routers.
6. Exchange - the router is sending data description packets to the neighbor.
7. Loading - Link state request packets are sent to the neighbor.
8. Full - the neighboring routers are fully adjacent.