Juniper IGP - CONFIGURATION GUIDE V11.1.X Configuration Manual page 291

You can optionally define an area to be a stub area, totally stubby area, or a
not-so-stubby area. You can configure virtual links for areas that are not directly
connected to a backbone area.
area default-cost
area nssa
NOTE: We recommend that you do not use the default-information-originate
keyword with the no-summary keyword for an NSSA.
Creating areas complicates the task of configuring OSPF routing domains.
Use to configure the cost for the default summary route sent into a stub area.
Cost is a metric value in the range 1–65535; the default value is 1.
Use only on an ABR attached to a stub area.
Provides the metric for the summary default route that the ABR generates into
the stub area.
Example
host1(config-router)#area 47.0.0.0 default-cost 1
Use the no version to remove the configured default route cost.
See area default-cost
Use to configure the area as an NSSA.
You must configure each router in a stub area as belonging to the stub area.
An NSSA is like a stub area, but it can also import external AS routes in a limited
way.
To cause NSSA border routers to generate a type 7 default LSA in the OSPF
database if there is a default route in the routing table, you must specify the
default-information-originate option.
You can specify a metric cost, metric type, or a route map to be applied to the
generated type 7 default LSAs.
Use the no-summary keyword to create a "totally stubby area" and restrict type
3 summary LSAs from flowing into the area. However, type 3 default-route LSAs
can continue to flow into the area and a type 3 default-route LSA is advertised
into the NSSA.
Example
host1(config-router)#area 35.0.0.0 nssa
Use the no version to remove the NSSA designation from the area, to stop the
generation of type 7 default LSAs, to reinitiate type 3 summary LSAs into the
Chapter 5: Configuring OSPF
Configuring OSPF Areas
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