Editing Open Shortest Path First (section)

===Adjacency state machine===
Each OSPF router within a network communicates with other neighboring routers on each connecting interface to establish the states of all adjacencies. Every such communication sequence is a separate ''conversation'' identified by the pair of router IDs of the communicating neighbors. RFC 2328 specifies the protocol for initiating these conversations (''Hello Protocol'') and for establishing full adjacencies (''database description packets'', ''link-state request packets''). During its course, each router conversation transitions through a maximum of eight conditions defined by a state machine:<ref name="rfc2328"/><ref>{{cite web |url=http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13685-13.html |title=OSPF Neighbor States |website=Cisco |access-date=2018-10-28 |archive-date=October 26, 2018 |archive-url=https://web.archive.org/web/20181026025203/https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13685-13.html |url-status=live }}</ref>

====Neighbor state changes====
[[File:OSPF-Adjacency-process.drawio.png|thumb|Neighbor state changes (Hello Protocol)]]
#Down: The state ''down'' represents the initial state of a conversation when no information has been exchanged and retained between routers with the Hello Protocol.
#Attempt: The ''attempt'' state is similar to the ''down'' state, except that a router is in the process of efforts to establish a conversation with another router, but is only used on [[non-broadcast multiple-access network]]s (NBMAs).
#Init: The ''init'' state indicates that a hello packet has been received from a neighbor, but the router has not established a two-way conversation.
#Two-way: The ''two-way'' state indicates the establishment of a bidirectional conversation between two routers. This state immediately precedes the establishment of adjacency. This is the lowest state of a router that may be considered as a DR.

====Database exchange====
[[File:OSPF-Adjacency-process-Neighbor state changes (Database Exchange).drawio.png|thumb|Neighbor state changes (database exchange)]]
#Exchange start (exstart): The ''exstart'' state is the first step of adjacency of two routers.
#Exchange: In the ''exchange'' state, a router is sending its link-state database information to the adjacent neighbor. At this state, a router can exchange all OSPF routing protocol packets. 
#Loading: In the ''loading'' state, a router requests the most recent [[link-state advertisement]]s (LSAs) from its neighbor discovered in the previous state.
#Full: The ''full'' state concludes the conversation when the routers are fully adjacent, and the state appears in all router- and network-LSAs. The link-state databases of the neighbors are fully synchronized.