c589b6fa_pen_Shortest_Path_First__OSPF___Description
[Type #] 7 [LSA Name] NSSA External [Description] 
OSPF stub areas are those without a direct path to the outside; they do not allow Type 5 LSAs in, and all externally bound traffic is just routed out through the stub area’s boundary router. A “not so stubby area” (NSSA) has some limited external routes available; they are advertised within the NSSA using Type 7 LSAs. The NSSA’s boundary routers translated Type 7 LSAs into Type 5 LSAs to flood into adjacent areas.
Types of link-state advertisements (LSAs) used in Open Shortest Path First (OSPF)
Description