OSPF seven neighbor states

1: down state: ospf has not been turned on yet
2: init: initialization state, the first time a hello message is received from the peer, at this time it will The status of the end is set to the init state
The role of the hello message: discovery, establishment and maintenance of neighbor relationships
When the router in ospf wants to exchange link status information, A neighbor relationship needs to be established. This relationship is achieved through hello messages. After the neighbor relationship is established, hello messages are sent periodically to maintain the neighbor relationship. If no hello messages are sent for a period of time, the neighbor relationship will be interrupted< /span>
a> At this time, the neighbor status between RTA and RTB becomes Full, indicating that the complete adjacency status is reached. 7. RTA sends an L SACK message to RTB to confirm the received SA. 6. After the neighbor status changes to Loading, RTA begins to send L SR messages to RTB, requesting Those link status information discovered through DD packets in Exchange state and not in the local LSDB. After receiving the LSR message, RTB sends an LSU message to RTA. The LSU message contains detailed information about the requested link status. After receiving the LSU message, RTA changes the neighbor status from Loading to Full. Even if RTA does not need a new DD message to describe its own LSD.B, as a slave router, RTA needs to respond to every DD message sent by the master router RTB. Undergo verification. Therefore, RTA sends a DD message with empty content to RTB. After sending the last DD message with sequence number Y+1, RTA changes the neighbor status to Loading; after RTB receives the last DD message, it changes the status is Full (assuming that RTB's LSDB is the latest and most complete, and there is no need to request updates from RTA), 5. After the neighbor status changes to Exchange, RTB sends a new DD message, which contains the description information of L SDB, and the DD sequence number is set to Y+1 (last used The sequence number plus 1), RTA sends a new DD packet, which contains the summary information of LSDB. The sequence number is set to the sequence number used by RTB in step 2, so RTB changes the neighbor status Change to Exchange. RTB also sends the first DD message to RTA. In this message, the DD sequence number is set to Y (assumed). RTB also declares itself as the master router. Since the Router ID of RTB is larger than that of RTA, RTB should be the real main router. After the neighbor status changes to ExStart , RTA sends the first DD message to RTB. In this message, the DD sequence number is set to X (assumed), and RTA declares itself as the master router. Enter the exstar state and determine the master and slave routers by sending DD packets 4: Start database synchronization after the neighbor relationship is established 3: In the two-way state, both parties establish communication with each other and receive each other's hello messages to establish neighbor relationships neighbor list representation of neighbor router id This router has received the legal hello message from the neighbor router router priority is used to elect DR and BDR router deadinterval The death time is usually 4 times the update time hellointerval update time
networkmask: the network mask of the interface that sends hello messages Some important fields in hello messages

OSPF seven neighbor state machines_ospf neighbor state machine_a blog that will never grow old in the world-CSDN blog1: down state: ospf has not been turned on yet 2: init: In the initialization state, the hello message sent by the peer is received for the first time. At this time, the state of the peer is set to the init state. The role of the hello message: discovery, establishment and maintenance of neighbor relationships. In ospf, the router needs to perform link status information When exchanging, a neighbor relationship needs to be established. This relationship is realized through hello messages. After the neighbor relationship is established, hello messages are sent periodically to maintain the neighbor relationship. If no hello messages are sent for a period of time, this neighbor relationship... .https://blog.csdn.net/cornerlin/article/details/105398244