LSAs are classified by type. Each type serves a different purpose and some are described in the following list:
Router LSAs (type 1)— Contain information about a router and the links it has in an area; they are flooded within an area only. The router indicates if it can compute paths based on Quality of Service (QoS), if it is an area border router, if it is one end of a virtual link, or if it is an autonomous system boundary router (ASBR) within this LSA. Type 1 LSAs are also used to advertise stub networks, which have only one router attached.
Network LSAs (type 2)— Used for transit networks within an area; they are not flooded outside of an area. A transit network has at least two routers connected.
Summary LSAs for ABRs (type 3)— ...