A Type 2 link-state advertisement (LSA) contains subnet and router information for all the routers on a segment. Type 2 LSAs, which are also called network LSAs, are generated by only the designated router (DR) to each of the segments connected to the DR. These LSAs are not propagated outside the area in which they originate? they are flooded only within the local area.

A Type 1 LSA contains router ID and interface IP address information for a single router. Type 1 LSAs, which are also called router LSAs, are generated by all Open Shortest Path First (OSPF) routers on a segment. Like Type 2 LSAs, Type 1 LSAs are not propagated outside the area in which they originate; they are flooded only within the local area.

A Type 3 LSA contains subnet information for an entire area. Type 3 LSAs, which are also called network summary LSAs, are generated by area border routers (ABRs). Unlike Type 1 and Type 2 LSAs, Type 3 LSAs are advertised between areas throughout an autonomous system (AS) except into totally stubby areas.

A Type 5 LSA contains subnet information for an external AS. Type 5 LSAs, which are alsocalled ASexternal LSAs, are generated by autonomous system boundary routers (ASBRs). Therefore, Type 5 LSAs are advertised throughout an AS except into stub areas, totally stubby areas, and not so stubby areas (NSSAs).