Which OSPF Message Type is used to request link-state information from neighbors?

In OSPF (Open Shortest Path First), the Link-State Request (LSR) message is specifically designed to request link-state information from neighboring routers. When a router discovers that it needs more information about the link states it has received, it will send an LSR message to its neighbors. This mechanism allows a router to actively gather the required topology data to build or update its link-state database.

The use of LSR messages ensures that a router has the most current and accurate information available from its neighbors, which is crucial for effectively determining the best paths through the network. This process is part of OSPF's operation to maintain an up-to-date view of the network topology, enabling efficient routing decisions.

In the context of the other message types, Database Description (DBD) messages are used to describe the contents of a router's link-state database. Link-State Updates (LSU) contain the actual link-state advertisements that are shared between routers. Lastly, Link-State Acknowledgements (LSAck) are sent to confirm the receipt of LSU messages. Each of these message types plays a vital role in OSPF operation, but the specific purpose of requesting link-state information is fulfilled by the LSR message.