What happens to the link-state database if a router loses its connection to a neighbor?

When a router loses its connection to a neighbor, the link-state database becomes stale until the connection is restored. This is because OSPF (Open Shortest Path First) relies on neighbor relationships to share routing information dynamically. When a link is lost, the router no longer receives updates about the state of that link, and consequently, it cannot obtain fresh information about the topology around that neighbor.

During this stale period, the OSPF router continues to maintain its existing view of the network as represented in the link-state database. However, the stale database will not reflect any changes in the network that could have occurred while the connection was down, such as new routes being advertised by the neighbor or changes in the state of existing routes. Once connectivity is restored, the router will exchange information with the neighbor to re-sync the databases if necessary, ensuring that the link-state database reflects the current network topology.

This mechanism is crucial for maintaining the integrity and accuracy of the routing process within an OSPF area, preventing disruptions in route calculation based on outdated information. Thus, describing the link-state database as becoming stale captures the essence of its behavior in the face of a lost connection.