9tut ccna question

9tut ccna question.. Router Exchange.LSA within the LSU message.At the end, the routers reach the mu state, which means they have completely exchanged their LSDB contents.Full FullFigure 8-3 Example of a database exchange ending in the Full state LSU,with several LSAs Maintaining neighbors and LSDB Loading LSU,with several LSAs However, neighborsOnce the neighbors have reached the fiill state, they have done all the initial work of exchanging OSPF information between the two neighbors. A Loading residence must also perform a few minor daily tasks to maintain the neighbor relationship.First, the router monitors each neighbor relationship using Hello messages and two associated timers: HelloInterval and DeadInterval. every HelloInterval, the router sends a Hello to each neighbor. each router expects to receive a Hello from each neighbor every HelloInterval. Each router expects to receive one Hello from each neighbor every HelloInterval, so if a neighbor's silence time reaches the length of the Dead Interval (by default, four times the length of the HelloInterval), the loss of a Hello means that the neighbor has failed.Next, the router must also react when the topology changes, and neighbors play a key role in this process. When a change occurs, one or more routers modify one or more LSAs. the router must then flood the modified LSAs to each neighbor, allowing the neighbor to modify its LSDB.For example, suppose a LAN switch loses power, so the router's G0/0 interface fails, going from up/up to down/down. the router updates an LSA to show that the router's G0/0 is down. the router then sends the LSA to its neighbors, who in turn send the LSA to their neighbors, until all routers have the exact same copy of the LSDB again. LSDB copy again. Each router's LSDB now reflects the fact that the original router's G0/0 interface failed, so each router will use SPF to recompute any routes affected by the failed interface.The third maintenance task performed by neighbors is to occasionally re-flood each LSA even when the network is completely stable. by default, each router that created the LSA is responsible for re-flooding the LSA every 30 minutes (the default) even if no changes have occurred. (Note that there is a separate timer for each LSA based on when it was created, so there is no one big event of the network being overloaded by a flooded LSA.)