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With IP there are two Link-State protocols in use, OSPF and IS-IS (Intermediate System to Intermediate System). Both work in pretty much the same way, but OSPF is more commonly used.
In an OSPF router, the topology database is referred to as the Link State Database (LSDB). The LSDB contains the detailed information that a router has regarding the topology of the internetwork. Each entry in the LSDB is called a Link State Advertisement (LSA).
When a new neighbor is found, an OSPF router’s goal is to synchronize its LSDB with that of the neighbor. By synchronize, we mean make the LSDBs consistent, so that they contain the same LSAs. To accomplish this, the routers compare LSDBs and any LSA that a router is missing, it requests from the neighbor.
Read on to learn more about OSPF synchronization.