Not-so-stubby-area (NSSA)
Beginning with software release K.12.xx, this
area is available and connects to the backbone area through one or
more ABRs. NSSAs are intended for use where an ASBR exists in an area
where you want to control the following:
Advertising the ASBR's external route paths to the backbone area
Advertising the NSSA's summary routes to the backbone area
- Allowing LSAs from the backbone area to advertise in the NSSA:
Summary routes (type-3 LSAs) from other areas
External routes (type-5 LSAs) from other areas as a default external route (type-7 LSAs)