LSA Flooding
Is the method by which OSPF shares its routing information, using LSU (Link State Update) packets.
Using the LSU’s, LSA’s with link state data is shared among all OSPF routers. The network topology is, then, created from these LSA updates.
Flooding is used so that all OSPF routers have the topology map from which SPF calculations can be made.
Efficient flooding is done through the reserved multicast address, 224.0.0.5 (AllSPFRouters).