Which OSPF packet type is used to share routing information between routers?

The OSPF packet type that is primarily used to share routing information between routers is the Link State Update (LSU) packet. This packet carries Link State Advertisements (LSAs), which contain detailed information about the network topology, including information about routers, their interfaces, and the state of those interfaces.

When routers use OSPF to communicate, they exchange LSUs as part of the process of building and maintaining a synchronized view of the network's topology. The LSU packets allow routers to receive updates about the state of links and routes from their neighbors, facilitating the creation and updating of the OSPF link-state database. This database is crucial for the OSPF algorithm to compute the shortest path first (SPF) tree and to determine the best paths for routing traffic.

The mention of LSAs in this context emphasizes that while LSAs are indeed the contents of LSU packets, it is the LSU packet itself that is responsible for the communication of these advertisements across OSPF routers. Therefore, the role of LSU in the OSPF protocol is fundamental for the dynamic and efficient sharing of routing information.