What step involves a router flooding link-state information about its directly connected links?

The process of flooding link-state information about directly connected links is a crucial step in the OSPF (Open Shortest Path First) routing protocol. This activity occurs during the exchanging of link-state advertisements (LSAs), which is the correct answer to the question.

When OSPF routers form adjacencies, they share LSAs that contain information about the state of their interfaces and the metrics associated with those interfaces. This information is then flooded throughout the OSPF area to ensure that all routers have the same view of the network topology. By disseminating this information, routers are able to build a complete and consistent link-state database, which is essential for calculating optimal routing paths.

The other steps mentioned involve different phases of the OSPF process. Establishing neighbor adjacencies is the initial phase where routers identify each other and form relationships, which is necessary before exchanging LSAs can occur. Choosing the best route comes after the link-state information has been gathered and is based on the shortest path first (SPF) algorithm. Advertising new information typically pertains to the process of informing neighboring routers about changes in link states rather than the initial flooding of links.

Overall, the exchanging of link-state advertisements is fundamental to OSPF's operation, as